
Class T~U 4 kj? 

Book /T^ 

Copyright^ 



COPYRIGHT DEPOSIT. 



The Valve-Setter's Guide 



THE 



Valve -Setter's Guide 



A TREATISE 



ON THE CONSTRUCTION AND ADJUSTMENT OF THE 

PRINCIPAL VALVE GEARINGS USED ON 

AMERICAN LOCOMOTIVES 



BY 



JAMES KENNEDY 



NEW YORK: 

ANGUS SINCLAIR COMPANY 

114 LIBERTY STREET 



PRICE FIFTY CENTS 






Copyright by the 

ANGUS SINCLAIR COMPANY, 

1 9 10. 




C.CLA25645-4 



CONTENTS 



3hapter page 

Preface 7 

I The Steam Engine 9 

II The Slide Valve 12 

III The Link Motion • • 14 

IV Adjusting the Stephenson Valve Gear 18 

V The Walschaerts Valve Gear 27 

VI Variations in Form in the Walschaerts Valve Gear 30 

/I I Construction of the Walschaerts Valve Gear 33 

/III Adjusting the Walschaerts Valve Gear 38 

IX The Baker-Pilliod Valve Gear 42 

X Construction of the Baker-Pilliod Valve Gear 44 

XI Adjusting the Baker-Pilliod Valve Gear 48 

XII The Joy Valve Gear 51 

Note on Setting the Slide Valve of a Stationary Engine. 56 



PREFACE 



It would be difficult indeed to write anything particularly new on a 
subject that has been so much commented on as the valve gearings of steam 
engines ; but it will be readily admitted that things that are already familiar 

to us may be seen in a new light. It will also be observed that in this age 
of rapid changes even the steam engine is found to be capable of improve- 
ment. The recent application of the Walschaerts valve gear to American 
locomotives, and also the more recent invention of the Baker-Pilliod valve 
gear has given a new interest to the subject. It is to be hoped the result 
will be that a greater degree of reliability in the harnessing of steam in 
locomotive service will be accomplished. It is with the hope of adding 
something to the general mass of information, especially with a view of 
being helpful to young railway men, that these articles have been written. 

Other valve gearings claim attention. Many others besides those de- 
scribed in this little book are in successful operation. Some still in embryo 
are full of promise. In selecting those that are the most popular forms 
of locomotive valve gearings in use in America, it is not with the intention 
of ignoring or belittling other ingenious devices, but with the assurance 
that a fair knowledge of the organic structure and methods of adjustment 

7 



THE VALVE-SETTER'S GUIDE 

of valve gearings commonly in use will readily help the thoughtful mechanic 
to a more easily acquired knowledge of the mechanism of any valve gear- 
ing, no matter in what shape the parts may appear. 

Not only so, but as the valve gearing is the most intricate part of the 
reversible steam engine, so the study of valve gearing is calculated to de- 
velop the faculty of giving thoughtful attention to the details of all forms of 
involved mechanism. 

A word may be added in regard to the brevity with which the subject has 
been treated. In an experience of many years among apprentice machinists 
and young railway men, I never found it advantageous to pour a mass of 
tedious information into the ears of listeners however willing they might be 
to hear. In fact, the more anxious they were to learn the less they needed to 
be told. A hint in the right direction was generally enough. Many excep- 
tions arise in practice which can hardly be foreseen in imagination. The in- 
telligent mechanic or engineer learns much that does not appear in print. 
Practical experience unfolds the mysteries of all arts. The object of a book 
of this kind should be to help the beginner to help himself. In the hope of 
aiding in kindling this noble aspiration these brief articles were written for 
the pages of Railway and Locomotive Engineering and met with much 
popular favor, and are now collected in more convenient form in the belief 
that they may be of further service to railway men. J. K. 

New York, Jan. 1, 1910. 






8 



THE STEAM ENGINE 



I. THE STEAM ENGINE 



Apart from the many varieties of form 
in which steam engines are made, there 
are two general divisons into which they 
may be classified, those of the condensing 
and non-condensing engines. The loco- 
motive and nearly all the factory engines 
are of the non-condensing type. In this 
class the steam after it has done its work 
in moving the piston, is exhausted into 
the open air. An engine of this kind is 
readily discerned by the puffing sound of 
the exhausted steam, each re-percussion 
indicating the completion of the piston 
stroke, and sudden release of the pent-up 
steam, which it may be observed has still 
much more than sufficient force left in it 
to overcome the pressure of the atmos- 
phere. In a condensing engine the steam 
after passing through the cylinder is ad- 
mitted into a box or receptacle called a 
condenser on account of its being cooled 
by contact with water or with pipes 
through which cold water is passing. The 
condensation of the exhausted steam has 
the effect of producing a partial vacuum 
in the condenser, which permits the steam 
being used until it has reached a lower 
pressure than in a non-condensing engine. 
Marine engines are mostly of this type, 
as a constant supply of cold water can 
readily be obtained. 

It will be remembered that the atmos- 



pheric engine previous to James Watt's 
invention of the steam engine, was oper- 
ated by the admission of steam into a 
vertical cylinder, while the piston was at 
the upper end of the stroke and when a 
jet of cold water was admitted into the 
cylinder, the steam was condensed, thereby 
producing a vacuum and the weight of 
the atmosphere acting on the uncovered 
upper face of the piston was sufficient 
to press down the piston. Watt con- 
ceived the idea of condensing the steam 
in a separate vessel, thereby effecting a 
great saving and also made the important 
advance in applying steam alternately to 
both sides of the piston, thereby creating 
or inventing an entirely different engine 
from that of Newcomen. 

The rapid condensation of steam into 
water renders suitable openings into all 
steam cylinders a necessity. These open- 
ings, or cylinder cocks, as they are called, 
are usually operated by a hand lever 
which is placed in the open position when 
starting the engine. This should be care- 
fully attended to, as water unavoidably 
gathers in the cylinders while engines 
are not running, that is if a pressure of 
steam is in the boiler. 

The most important openings into the 
cylinder, however, are the ports by which 
the steam is admitted and that bv which 



THE VALVE-SETTER'S GUIDE 



it escapes after its work is accomplished. 
This leads us to the slide valve, the most 
common form of valve used in steam en- 
gines, and although simple in construction 
it is a most ingenious contrivance for ad- 
mitting and cutting off the supply of 
steam at the desired instant of time. The 
cylinder is so constructed as to form a 
flat portion on a part of its outer surface 
on which there are three rectangular 
openings, the middle being the exhaust 
port, is wider than the other two, and 
leads directly from the cylinder face to 
an opening on which the exhaust pipe 
may be bolted. The two other ports are 
the steam ports, one leading to one end 
of the cylinder and the other to the other 
end. The slide valve is so constructed 
as to cover these three openings and is 
shaped like a hollow rectangular dish 
with an inner cavity, the edges of the dish 
forming the face of the valve. This face 
is carefully fitted so that when the valve 
is placed in position it forms, in conjunc- 
tion with the surface of the cylinder, a 
steam-tight joint. It may be added that 
in the early days of the steam engine 
much care was taken in fitting the valve 
face and valve seat together so that every 
part of the metals were bearing equally 
on each other. It was latterly found that 
the friction incident to the movement of 
the valve very quickly caused the valve to 
adjust itself to the valve seat so that a 
fine bearing at the start is not essential, 
the bearing being perfected in the course 
of a few hours' service. 

The slide valve, when in the central 
position, covers the two steam ports and 



leaves the middle port open in the inner 
cavity of the valve. If the valve was so 
constructed as to cover the two steam 
ports exactly it can be readily perceived 
that a movement of the valve in either 
direction would open one of the steam 
ports leading to the cylinder and open 
the other steam port to the inner cavity of 
the valve, thereby opening the communi- 
cation to the exhaust pipe. A valve so 
constructed would admit steam during the 
entire length of the piston stroke, so that 
when the piston stroke was completed the 
steam in the cylinder would be at or near 




FIG. i. SLIDE VALVE WITHOUT LAP. 

boiler pressure and when released by the 
opening of the exhaust port, as already 
alluded to, the loss of steam at each stroke 
would be equal to the full capacity of the 
cylinder and steam spaces. In its primi- 
tive form the slide valve was constructed 
in this way and was used on some of the 
earlier engines of James Watt. Fig. I 
shows such a valve in the central position. 
This form of valve had several serious 
objections. The smallest degree of lost 
motion had the effect of admitting the 
steam in a sufficient quantity to obstruct 
the piston at the end of the stroke. The 
tendency to create severe pounding was 



10 



THE STEAM ENGINE 



very great. The most important draw- 
back was in the fact, already alluded to, 
that the steam was released while at full 
pressure, and no advantage could be taken 
of the expansive power of steam. Dur- 
ing Watt's lifetime the pressure of steam 
as applied to steam engines was extremely 
low, so that the loss was not so very great 
as it became when, with the improvement 
in boiler construction, higher pressures of 
steam became available. • In the early days 
of the locomotive fifty pounds pressure of 
steam per square inch did not admit of 
much advantage being taken of the ex- 
pansion of steam in the cylinder. The 
change of the form of the slide valve was 
very simple, but very important. It con- 
sisted merely of lengthening the valve 
face, so that when the valve stood in the 
center of the seat the edges of the valve 
extended a certain distance over the steam 
ports, as shown in Fig. 2. 

This extension of the valve faces is 
called outside lap, or simply lap. It has 
the effect of closing the steam port at a 
certain distance before the piston reaches 



the end of the stroke, and this point, 
which with the variations incident to the 
action of the radial link is a variable 
point, usually called the point of cut-off. 
It can be readily understood that when 
the supply of steam is cut off from the 
boiler before the piston stroke is com- 




FIGu 2. VALVE WITH OUTSIDE LAP. 

pleted, the piston is moved on its further 
course by the expansive power of steam, 
and when the stroke is completed the 
steam in the cylinder having increased 
in volume is correspondingly reduced in 
pressure and when released the loss is not 
great, as the pressure of the steam is not 
greatly in excess of the pressure of the 
atmosphere. 



II 



. THE VALVE-SETTER'S GUIDE 



II. THE SLIDE VALVE 



Having described the construction of 
the slide valve and its relation to the 
steam ports, and pointed out the advan- 
tage derived from the face of the valve 
being made more than sufficient to cover 
the steam ports, it remains to be stated 
that the opening and shutting of the 
steam ports by the movement of the 
valves is of the utmost importance in the 
running of the steam engine. It will be 
readily understood that when the piston 
is at one or other of the extreme ends of 
the cylinder and it is intended that it 
should be moved in the other direction, 
the steam port should be rapidly opened 
so that the steam may exert its full pres- 
sure on the face of the . piston. Many 
eminent engineers held the opinion that 
the opening of the port should occur in 
advance of the arrival of the piston at the 
end of the stroke. This is what is known 
as the lead of the valve. It has been the 
subject of much discussion and is still an 
open question. At first sight it would ap- 
pear to be a hindrance to the piston to 
meet with a pressure of steam working 
adversely to the direction in which the 
piston was moving, but when it is borne in 
mind that even steam at high pressure, 
moving at a high velocity, requires some 
small instant of time to move through 
the intervening space between the steam 



chest and cylinder, and also that the pis- 
ton itself may be moving at a high speed, 
it is easy to understand that it may be 
an advantage to begin to open the valve 
slightly in advance of the reversing of the 
movement of the piston. 

This is more readily apparent in the 
case of engines running at high speeds 
than otherwise, because the velocity with 
which the steam moves through a certain 
space at a certain pressure may be safely 
called a constant velocity, while the rate 
of speed at which the valve or the pis- 
ton travels varies according to the kind 
of work accomplished. This fact has led 
to the claim that the increase in the 
amount of lead in the valve which is 
caused by the shortening of the travel of 
the valve in the case of engines equipped 
with the Stephenson valve gear is an ad- 
vantage to locomotives running at high 
speeds when the reverse lever is "hooked 
up." The action of the steam in striking 
with sudden force at the beginning of the 
piston stroke may be likened to what is 
known as "advancing the spark" in gaso- 
line engines, which has the effect of in- 
creasing the velocity of the engine partly 
from the more complete compression of 
the inflammable gases, and partly from 
the fact that the gasoline engine piston 
receives the full shock of the explosion 



12 



THE SLIDE VALVE 



before it has moved any considerable dis- 
tance from the end of the cylinder. 

The parallel between the action of 
steam pressure and gasoline explosion, 
however, is not an exact one. The varia- 
tion is very great, steam being a constant 
pressure and gasoline explosion an inter- 
mittent shock. Increasing the amount of 
lead in the valve of a steam engine does 
not by any means increase the speed of 
the engine. It has the contrary effect, 
and it is a growing fact that the idea 
which obtained in many quarters that a 
locomotive could not run freely unless 




SLIDE VALVE SHOWING LEAD. 

the valves were set with considerable lead 
is rapidly losing its adherents. This fal- 
lacy may readily be dispelled by marking 
the degree of smoothness with which a 
well-balanced locomotive will run when 
an opportunity occurs to shut off steam 
altogether. The alleged shock which a 
certain amount of lead of the valve is 
said to overcome is not apparent, and 
there is undoubtedly a growing opinion 
that the older methods of having a valve 
opening of one-eighth of an inch is grad- 
ually losing ground, and this amount after 
being cut down to one-sixteenth is now 



reaching the thirty-second mark, and if 
the present trend of thought continues the 
so-called lead of the valve will have be- 
come a minus quantity. 

It may be added that the idea that the 
increase in the amount of lead of the valve 
caused by the shortening of the valve 
travel, in the case of the Stephenson 
valve gearing, was an advantage, has lost 
credence largely from the fact that since 
the rapid introduction of the Wal- 
schaerts valve gearing, with which many 
of the new and larger locomotives are 
equipped, it has been clearly demonstrated 
that the constant lead maintained by the 
latter valve gearing at varying amounts 
of valve travel and speed, is a decided 
advantage in its favor. Indeed, many 
experienced engineers do not hesitate to 
assert that the excessive amount of lead 
formerly allowed in locomotive practice, 
and the large increase in that amount oc- 
casioned by the shortening of the valve 
travel, was the chief cause of much of the 
troubles incident to the involved mechan- 
ism of the Stephenson valve gearing. Be 
this as it may, the opinion is rapidly tak- 
ing firm root that the amount of valve 
opening at the end of the piston stroke 
should be kept at the lowest possible 
amount, and that better results in loco- 
motive and engine running generally could 
be obtained by having the valve closed 
at the end of the piston stroke than by 
having an opening wide enough to admit 
sufficient steam that cannot do other than 
counteract the motion of the piston as it 
approaches the dead center. 



13 



THE VALVE-SETTER'S GUIDE. 



III. THE LINK MOTION 



A peculiarly important quality of the 
steam engine is the fact that it lends itself 
with ease to perfect control. That mo- 
tion of such amazing force can be sud- 
denly stopped and reversed within a brief 



ments are simple enough, and if taken 
into consideration one by one can be 
readily understood by the average student 
in a short time. 
The invention of the link motion has 




U Valvt 8tm 




BockerSha/t 



a* Central Lint of Motion 
% 



period of time is one of the most won- 
derful results of applied science. 

The most common form of reversing 
gear is what is known as the link motion. 
The combination of levers and rods and 
eccentrics and radial link have an involved 
air of mystery to the young engineer, but 
a little attention will show that the move- 



been the subject of much controversy, but 
it is now universally conceded that Mr. 
William Williams, a young Welchman, a 
draughtsman employed in the Stephenson 
Locomotive Works at Newcastle, Eng- 
land, submitted the first sketch showing the 
idea of a movable link suspended from 
the arm of a movable shaft and equipped 



14 



THE LINK MOTION 



with means of being attached to two ec- 
centrics, the movable link being attached 
to the valve rod, effecting the reversing 
of the engine and also a variation in the 
valve travel and consequent variation in 
the expansive use of steam. It was a 
masterly invention and the unconscious 
young inventor, to whom the thought had 
come as an inspiration, had evidently no 
comprehension of the momentous impor- 
tance of the device. It may be said to 



explained his device to some self-seeking 
shopmates who were not slow to take ad- 
vantage of his ingenuousness. Claims of 
improvements were made by others, but 
the fact is that Mr. Williams' finished in- 
vention was incapable of any improve- 
ment. The device was not patented. The 
Stephensons began applying it to their 
locomotives in 1842. It came into im- 
mediate favor and has been the most 
popular form of valve gearing used on 




&)■ i l *co. fry. 



REPRESENTATION OF THE ANGUS SINCLAIR CO. VALVE MODEL WITH D-SLIDE 

VALVE. 



have completed Watt's wonderful engine. 
At one stroke the harnessing of the titanic 
force of steam was completed. Engines 
could henceforth be run backward or for- 
ward. Variable expansion, variable speed, 
with all the delicate varieties in force and 
velocity, were at once accomplished. 

It is a matter of regret that so little is 
known of the gifted mechanician. With 
the frankness of youth he seems to have 



locomotives ever since. In the absence of 
any legal claim to the invention the device 
became generally known as the Stephen- 
son valve gearing or shifting link, the 
latter name being used in contradistinction 
to link motions where the link oscillates 
on a fixed center as in the Walschaerts 
valve gearing. 

In the excellent model before us, a du- 
plicate of which can be procured from the 



IS 



THE VALVE-SETTER'S GUIDE 



publishers of Railway and Locomotive 
Engineering, and a drawing of which is 
reproduced for illustration, it will be noted 
that the piston is in the middle of the 
cylinder. Both steam ports are closed, 
and if it is desired that the engine should 
be moved forward it will be necessary that 
the steam be admitted at the front so that 
the piston should be pressed backwards 
and so move the wheels forward on the 
rails. In order to admit the steam to the 
front end of the cylinder the valve must 
be moved backward. It will be readily 
noted that by moving the lever forward 
on the quadrant the radial link is dropped 
downward until the upper eccentric rod 
is in line with the lower end of the rocker. 
To accommodate itself to this movement 
the lower end of the rocker has been 
pushed some distance forward, the upper 
end of the rocker consequently moving an 
equal distance backward and carrying with 
it the slide valve. This has the effect of 
opening the steam port leading to the 
front end of the cylinder and the pressure 
of the steam is admitted to the front face 
of the piston. 

If, on the other hand, it is desired to 
move the engine backwards, it will be 
found that by moving the lever to the 
back of the quadrant, the link is raised 
until the lower eccentric is in line with 
the lower end of the rocker. To admit 
of this movement the lower end of the 
rocker is drawn back with the consequent 
result that the upper end of the rocker 
has been moved a corresponding distance 
forward, thereby opening the steam port 
leading to the back of the cylinder and 



so admitting the steam to the back of the 
movable piston, which moving forward 
has the effect of moving the wheels back- 
ward upon the rails. 

There are several important factors 
rendering these simple movements pos- 
sible and wTiich, if carefully observed, will 
readily impress themselves upon the mem- 
ory of the attentive student. The first is 
that with the rocker in perpendicular posi- 
tion, the valve rod should be of the exact 
length so that the valve should be in the 
central positon in regard to the steam 
ports. Presuming that the piston has 
moved forward in the cylinder until it 
has reached the extreme end of the stroke, 
it is necessary that the valve should be 
beginning to open the front port in order 
that the steam may be admitted to the 
front face of the piston for the purpose 
of moving the piston backward. At this 
particular point it is well to turn our 
attention to the position of the eccentrics 
and their relation to the driving crank. 
It will be understood that with the pis- 
ton at the front end of the cylinder the 
main crank pin is at the forward center. 
If the valve was so constructed as to 
cover the steam ports exactly, the two ec- 
centrics should be standing with their 
extreme points at right angles to the main 
crank pin, the forward eccentric with its 
extreme point being on the top or above 
the crank, and the eccentric controlling 
the backward motion on the bottom or 
below the crank. 

As previously described, however, the 
valve in modern use is so constructed that 
the extreme ends of the valve when in a 



16 



THE LINK MOTION 



central position overlap the steam ports. 
In the modern locomotives this amount 
of lap extends to three-quarters of an 
inch, and if to this is added some amount 
of valve opening it will be readily under- 
stood that the eccentrics must be moved 
sufficiently from the position at right 
angles to the crank to a position nearer 
to the crank by an amount equal to the 
lap and lead combined. The effect of this 
movement toward the crank on the part 
of the eccentric has the effect of pushing 
the lower end of the rocker toward the 
cylinder and consequently drawing the up- 
per end of the rocker with the valve rod 
backward a sufficient distance to overcome 
the lap of the valve. 

It need hardly be stated that the sliding 
valve alluded to is the common D-shaped 
valve, but the operations of the outside 
admission piston valve are identical with 
the action of the valve described. In the 
case of an inside admission piston valve 
a change of the position of the eccentrics 
in their relation to the main crank is nec- 
essary, as it will be readily seen that the 
edge of the valve at the point of admission 



is at the opposite side of the port and 
the valve also must necessarily travel in 
the opposition direction to that of the out- 
side admission valve. The relative merits 
of the various forms of valves are not 
pertinent to a general discussion of the 
link motion. 

It will be observed that the radial link 
is simply a contrivance for the purpose of 
detaching one eccentric and placing the 
other in operation, besides which it has 
the advantage of varying the amount of 
travel of the valve, thereby allowing a 
supply of steam to be admitted for a long 
cr short space of the piston stroke. This 
is accomplished by moving the lever 
toward the center of the quadrant and it 
will be easily understood that as the ec- 
centric rod in operation is moved some 
distance from the end of the rocker it has 
the effect of shortening the movement of 
the rocker arm and consequently shorten- 
ing the stroke of the valve. Such are the 
chief features of the link motion and with 
these clearly in mind, other less important 
details may be readily mastered by the 
thoughtful student. 



17 



ADJUSTING THE STEPHENSON VALVE GEAR 



IV. ADJUSTING THE STEPHENSON VALVE GEAR. 



The importance of correctly adjusting 
and maintaining the position of the valves 
cannot be overestimated. Like the valves 
in the hearts of animals their perfect 
operation is the very life of the moving 
force of the machine. The work of ad- 
justing the mechanism has been absurdly 
overestimated, and the idea assumed by 
many that the operation is a difficult one 
is a gross error. Like other alleged mys- 
teries that owe their importance to the 
lack of opportunity of witnessing their 
true inwardness, familiarity soon begets a 
spirit of common regard. There is just 
the same degree of accuracy necessary in 
adjusting the attachments of the throttle 
valve. Both are a simple matter of care- 
ful experiment and exact measurement. 
In adjusting the ordinary sliding valve it 
may be said at the outset that there are 
degrees of proficiency required from the 
designing of the parts of the gearing to 
the simple matter of squaring the eccentric 
rods in a brief roundhouse examination. 
The working machinist is very safe to 
assume that the designer's part is correct 
and he can safely proceed with the adjust- 
ment of the valve gear, which is generally 
among the last operations in the building 
or repairing of a locomotive. 

Assuming that the four eccentrics are 
loose upon the driving axle of an or- 



dinary 8-wheel locomotive, the best plan 
is to move the engine until one of the 
crank pins on the axle to which the ec- 
centrics are placed is on the forward 
center, that is the point nearest to the 
cylinder. We will assume this is on the 
right side. If the eccentric which is de- 
signed to move the engine in a forward 
direction is intended to be next the frame, 
the eccentric may be promptly put in 
place somewhere about 85 degs. above 
the line of the crank pin, the exact po- 
sition need not be ascertained at this 
time, the eccentric being temporarily held 
in place by one or more set screws. The 
"eccentric intended for the backward mo- 
tion is placed a simlar distance below the 
crank pin or center line of the axle. The 
eccentrics on the other side of the engine 
can be similarly attached temporarily in 
their places. Assuming that the links 
have been already attached to the rockers 
and the link hangers adjusted to the arms 
of the lifting shaft, the forward eccentric 
rod should then be adjusted to the top of 
the link and the back eccentric rod to the 
bottom of the link. We are now ready to 
begin the operation of correctly adjusting 
the entire gearing, and it may be stated 
that inasmuch as the preparatory mark- 
ings of centers and openings are of prime 
importance, it is proper that the locomo- 



ADJUSTING THE STEPHENSON VALVE GEAR 



tive should be levelled. It does not follow 
that because the engine is new or newly 
repaired it is exactly level. The tendency 
is to drop slightly in front, which is gen- 
erally rectified when the water is placed 
in the boiler. When the engine is level 
the rocker should be placed exactly plumb. 
This can readily be done by moving the 
reverse lever while a fine line is hung 
over the rocker end with two small 
weights attached and the lever stopped at 
the exact point where the two lines are 
equidistant from the center of the rocker. 
The valve rod should then be adjusted 
so that the valve is exactly in the middle 
of the valve seat. A neglect of this im- 
portant point will cause variations in the 
valve travel that can never be entirely 
overcome. At this time it should be noted 
whether the valve yoke is properly ad- 
justed to suit the thickness of the valve, 
as in the case of an engine being fre- 
quently repaired the valves and valve 
faces wear rapidly and a liner may be 
necessary under the valve yoke to prevent 
undue strain upon the valve rod packing 
as well as a tendency to tilt the valve. 

Before finally attaching the valve rod 
to the rocker, the best method of marking 
the exact positon of the valve openings 
is by a tram reaching from the guide 
yoke or other fixed part of the engine to 
a suitable position on the valve rod. 
Both ends of the tram are sharpened, one 
end to adjust itself to a center punch 
mark on the guide yoke, and the other 
end, which is bent so as to scratch a mark 
readily on the valve rod. The points 
marked are necessarily where the valve is 



beginning to open at the front and back 
steam ports. The marks on the valve rod 
should be marked lightly with a fine cen- 
ter punch. The steam chest lid can then 
be put on the steam chest and any dan- 
ger of material or articles falling into the 
steam chest can be entirely avoided. 

The next operation should be the ascer- 
taining of the exact dead centers or po- 
sitions when the crosshead and piston are 
standing still at each end of the piston 
stroke. This point should be located very 
carefully. If the rim of the main driving 
wheel is near the guide yoke the same 
tram may suit to locate the center, but 
generally a longer tram is necessary with 
both ends bent. The engine may then 
be moved to a point where the crosshead 
is about half an inch from the back or 
forward end of the stroke. A fine center 
punch mark may be made on the cross- 
head and guide yoke or guide block as 
the case may be, and a pair of compasses 
carefully adjusted to the two points. Ac- 
companying this adjustment, the tram 
should be extended from the guide yoke 
or other point to the rim of the wheel 
and an arc drawn by the sharp end of 
the tram. The engine should then be 
moved over the center until the crosshead 
returns to the exact point where the com- 
passes touch the center marks on the 
crosshead and guide yoke or block. An- 
other arc or line should be drawn on 
the wheel rim and a point between those 
two arc lines is the dead center. It will 
be noted by those who have time to try 
the experiment that it is difficult to ob- 
tain this center mark in a positively cor- 



19 



THE VALVE-SETTER'S GUIDE 



rect positon. A repetition of the experi- 
ment with the crosshead at a greater or 
lesser distance from the end of the stroke 
will show a slight variation. This arises 
from the fact that while the crosshead is 
moving very slowly near this point the 
rim of the wheel is moving rapidly, and 
it may be added that the valve is also 
moving rapidly at this time. Hence the 
utmost care should be taken in ascer- 
taining the dead centers. It is often 
noted that in looking over the valves, it 
may be only a few days after the engine 
has been running, that the exact center, 
as newly discovered, may show a con- 
siderable variation in the rim of the 
wheel. This arises from the lost motion 
already caused by the incidental wear of 
the engine bearings, so that old markings 
on wheel rims instead of being of any 
value are often misleading. Variations in 
the dead center marks will also show in 
marking while the engine is moving for- 
ward as compared with markings that are 
made while the engine is running back- 
ward. 

It is seldom that the wheel rim varia- 
tions in marking are heeded, but they 
are of real value if a serious effort is 
maintained to keep the valves in correct 
positions. 

Having the valve rods marked and the 
dead center points located, we now pro- 
ceed to ascertain the position of the 
valves. As one at a time is good work, 
at least for a beginner, we may as well 
proceed with the right forward. Place 
the reverse lever in the extreme forward 
notch and mOve the engine forward' until 



the tram touches the dead center point. 
Then proceed to make a mark on the 
valve rod. If you are on the forward 
center observe if the mark made on the 
valve rod is near the forward opening 
mark. Keep in your mind's* eye the lo- 
cation of the end of the piston stroke 
and steam port you are working on. 
Move the engine ahead till you reach the 
other end of the stroke where it is as- 
sumed marks have been made on the 
wheel rim in the same manner as before. 
With the tram at the center try the tram 



F >l 



F 7\ 



FIG. i. FIRST MARKING. 

on the valve rod and make another 
scratch. It is not to be expected that 
the scratches will be equidistant from the 
marks showing the valve openings. We 
will suppose that Fig. I is about the 
location of the scratchings and opening- 
marks. 

It will be seen at a glance that the valve 
opening at the front end of the stroke is 
about three-eighths of an inch, while at 
the back end there is about one-eighth of 
an inch of lap, or in other words there 
is no opening at the back end of the 
stroke until the valve rod has moved at 
least one-eighth forward. It will readily 
be seen that no matter which end of the 
stroke we are at the valve rod must be 
moved about a quarter of an inch ahead 



20 



ADJUSTING THE STEPHENSON VALVE GEAR 



in order to equalize the opening at both 
ends of the stroke. Assuming that both 
ends of the rocker are of equal length, 
the right forward eccentric rod must be 
shortened a quarter of an inch. It is not 
necessary at this time to make the altera- 
tion perfectly exact, but we shall suppose 
that the rod is moved and that the open- 
ing on each end is about a quarter of an 
inch. Another trial of the tram at both 
ends should show something resembling 
Fig. 2. 

We will assume that the amount of 
opening desired at the end of the stroke 
is one-eighth of an inch. It will be seen 
that presuming we are at the front end 
opening the valve rod must be moved 
ahead one-eighth, but it must be evident 
that while moving the eccentric rod would 
accommodate us at this end of the valve 



r >i 



FIG. 2. ECCENTRIC ROD ADJUSTED. 

stroke, it would have the effect of in- 
creasing the opening at the other end, as 
was seen in the previous experiment, it 
is, therefore, necessary when the eccentric 
rod has been evenly adjusted that the ec- 
centric itself should be moved in order to 
increase or diminish the amount of open- 
ing at both ends of the valve stroke. In 
the present instance the eccentric must be 
moved further away from the crank and 
approach more nearly to right angles or 



90 degs. from the crank. While the 
eccentric is being moved, the valve rod 
should be carefully watched and the ec- 
centric secured at the desired point, 
which after experimentally moving the 
engine and marking the dead centers will 
show something like Fig. 3. 

Turning our attention to the backward 
movement of the engine, it is necessary 
to place the reversing lever in the notch 



F ^1 



1 



FIG. 3. ECCENTRIC ADJUSTED. 

furthest back and proceed with our ex- 
periments as before. Very likely the dis- 
crepancies will be greater than what is 
shown in Fig. 1, but the same methods 
will bring the desired results, and it will 
be noted that after having made the nec- 
essary changes on the backward eccentric 
rod and eccentric, the effect of the 
changes, in addition to bringing the open- 
ings of the valve to the desired amount, 
will have had the added effect of slightly 
changing the amount of openings on the 
forward motion. This is easily explained 
by the fact that in changing the position, 
of the eccentric or the length of the ec- 
centric rod the position of the link is 
slightly changed, thereby affecting the 
exact distribution of the motion in a 
ratio to the amount of change made. 
There are other disturbing causes that 
must not be overlooked. The length of 



21 



THE VALVE-SETTER'S GUIDE 



the reach rod is an important factor, and 
while the experiments are going on in 
regard to adjusting the eccentrics and 
rods, it is well to observe the amount 
of clearance that the link block has at 
each end of the link. It is safe to allow 
at least a quarter of an inch more clear- 
ance at the top of the link than at the 
bottom. In links where the amount of 
clearance is limited it is perfectly safe 
that the link block may approach within 
one-eighth of an inch when the link block 
is at the bottom of the link, as the 
tendency of the link is always to drop 
lower down as the joints begin to wear 
and as the heat expands the length of the 
boiler without materially expanding the 
length of the frames. 

Another important consideration is the 
fact that while the valves may be care- 
fully adjusted to open correctly at the 
-extreme length of the travel of the valve, 
it does not follow that when the lever 
is hooked up nearer the center of the 
•quadrant that the openings retain their 
exact ratio to each other. The tendency 
is in addition to increasing the amount 
t)f opening or lead as it is called, to create 
variations in the amount of opening at 
•each end of the valve stroke. In engines 
that are used with short valve travel, as 
in light running engines, it is often neces- 
sary to sacrifice the exact adjustment at 
the extreme end of the stroke in order 
that the valve openings may be squared at 
the point where the engine is called upon 
to perform most of its work. It need 
hardly be stated that the same remarks 
in detail apply to the left side of the en- 



gine, and that in common practice both 
sides are being adjusted while the engine 
is being moved or while the wheels are 
being revolved. 

It has already been noted that an ex- 
amination of the exact position of the 
valves after the engine has been running 
a short time will show more or less varia- 
tion corresponding in a great degree to 
the quality of the general workmanship 
exhibited in the construction or repair of 
the engine. Repeated examinations and 
readjustments are invariably necessary. 
The number and variety of joints through 
which the motion has to come before 
reaching the slide valve, renders the re- 
tention of the exact position of the valve 
for any length of time a physical im- 
possibility. 

Assuming that the rods and eccentrics 
have been carefully adjusted to suit the 
extreme travel of the slide valves and 
that it is necessary to adjust the amount 
of valve opening or travel at some 
hooked-up point, the common practice is 
to begin the operation by marking the 
extreme travel of the crossheads on both 
front and back end of the stroke. This 
can be readily done with a pencil marking 
a line on the guides. It is immaterial at 
what point we begin, but for simplifying 
the matter, suppose we begin as formerly 
at the right front end, and, moving the 
engine forward until the crosshead has 
moved six inches from the pencil mark, 
the valve tram can be used to locate the 
position of the valve. With the reverse 
lever in the front notch it will be found 
that the front steam port is wide open. 



22 



ADJUSTING THE STEPHENSON VALVE GEAR 



By drawing back the reverse lever the 
valve port is gradually closed and when 
the tram is exactly at the shut point on 
the valve rod the reverse lever latch 
should be dropped in the nearest notch 
and allowed to remain there. It is well 
to repeat the operation of finding the 
exact position of the valve by moving 
the engine a short distance backward and 
forward again to the point where the tram 
exactly enters the mark on the valve rod, 
showing that the steam port is at the clos- 
ing point. The distance from the extreme 
front end of the crosshead to the pencil 
mark on the guide may not be exactly 
six inches, but this is immaterial. Sup- 
pose it is 6y 2 ins., this should be marked 
down with chalk or otherwise and the 
operation continued on the other side of 
the engine in the same way and so on 
until the four separate and distinct dis- 
tances are discovered and marked down 
for reference. Suppose the right side 
shows 6y 2 ins. in front and 5^2 ins. in 
the back and that the left side shows 
7 ins. in front and 4^ ins. back. A gen- 
eral summing up of these distances would 
show that something near six inches 
would be the best average that could be 
obtained. Now if the link saddles are not 
new and are already bolted in place, the 
only course open to remedy the variation 
in the cut-off is to sacrifice the exact ad- 
justment of the eccentric rods and make 
such changes in raising one of the tum- 
bling shaft blocks or lowering one of the 
rocker boxes as may best meet the com- 
promise object at which we are darkly 
aiming. 



Returning to our familiar position on 
the right front where the distance from 
the crosshead to the pencil line is 6 l / 2 ins., 
suppose we stop the engine a little before 
we reach 6 ins., say 5% ins., and try the 
valve tram in order to ascertain how far 
we are from the valve opening mark. It 
will be found that there is probably y 32 of 
an inch of a valve opening at this point, 
and it will readily be seen that if the 
valve rod has to move forward a short 
distance in order that the tram will touch 
the mark as desired the shortening of the 
forward eccentric rod will have the de- 
sired effect. After effecting this slight 
change in the forward eccentric rod the 
crosshead distance from the pencilled lines 
on the guide can be again ascertained, 
and confining ourselves to the right side, 
suppose the distance at the front end 
shows 5% ins. and at the back end the 
distance is 6% ins., it is well to remember 
that a slight increase of the amount at 
the back end as measured from the cross- 
head to the pencilled line is a necessary 
arrangement in the case of a piston where 
the piston rod does not extend through 
the front cylinder head. 

In the case of the ordinary single-ended 
piston the variation in steam pressure at 
the different ends of the piston can be 
readily determined by calculating the area 
of the piston rod and deducting it from 
the area of the piston. Suppose the diam- 
eter of the cylinder is 20 ins., then 20 X 
20 X 7854 = 314.16 sq. ins., the area of 
the face of the piston. If the piston rod 
is 4 ins. in diameter then 4 X 4 X 7854 
= 12.56 ins., the amount to be deducted 



n 



THE VALVE-SETTER'S GUIDE 



from the area of the back end of the pis- 
ton. This is equal to one twenty-fifth of 
the entire area, and in any adjustment of 
the valve gearing this factor of pressure 
area should be considered. It would be 
very safe, therefore, to allow the figures 
to stand that we have already found on 
the right side and turn our attention to 
the important variation discovered on the 
left side. 

In this case where the difference in the 
measurement of the crosshead from the 
pencilled lines is much greater it would 
be inadvisable to adjust the eccentric rod 
so as to make up the entire difference. If 
we did so, it would be found that an ex- 
cessive amount of lead or valve opening 
would occur at one end of the stroke when 
the reversing lever was placed at the ex- 
treme end of the quadrant and there 
would be no opening at the other end of 
the stroke. Apart from this involved 
problem, another one equally important 
arises from the variation occurring in the 
amount of the distances at which the 
cut-off occurs. Even if it were advisable 
to adjust the eccentric rod to equalize the 
distribution of the amount of distance 
traveled by the piston at each end of the 
cut-off, the total amount at each end 
would still be greater than the distance 
already equalized on the right side. Now 
if we will observe the angle at which the 
link is hanging as held by the ends of the 
two eccentric rods it will readily be seen 
that if the link could be raised or the 
link block be lowered the effect would be 
to' move the lower end of the rocker arm 
towards the eccentrics while the valve rod 



would be moved. a corresponding distance 
in the opposite direction, thereby effect- 
ing an earlier closing of the valve. 

There are two methods by which this 
can be accomplished. A liner can be 
placed between the rocker box and frame 
or between the tumbling shaft block and 
frame. The effect in both cases is alike, 
although both remedies should be avoided 
if possible. A third remedy lies in the 
shortening of the link hanger, but this is 
a delicate and difficult operation, owing 
to the brittleness of the ends of the link 
hanger, and of the three evils the re- 
adjustment of the height of the rocker 
box is the best. The exact thickness of 
the liner can best be discovered by ex- 
periment. 

It need hardly be said that in the case 
of a new link, or new link saddle, the 
saddle can be temporarily adjusted and 
move experimentally to the correct posi- 
tion. It is usual in describing the exact 
location of the position of the pin by 
which the link is suspended to produce an 
array of figures and selections from the 
alphabet to illustrate the true position of 
the point of suspension. The illustrations 
and formulas are of little use, as is well 
known to all who have placed the parts 
of the Stephenson valve gearing in posi- 
tion, and in spite of the calculations hav- 
ing been very accurately made by the most 
accomplished mechanical engineers, there 
are almost invariably changes to be made 
in regard to the exact location of the link 
saddle pin. There are several causes that 
lead to this involved problem. The angu- 
lar advance of the main rods, together 



24 



ADJUSTING THE STEPHENSON VALVE GEAR 



with the same feature in the eccentric 
rods, have a singularly conflicting effect 
on the action that moves the rocker arm. 
It may be remarked that when the link is 
suspended exactly by the center of the 
link the large variation in the cut-off oc- 
curring under such conditions is caused 
largely by the angularity of the link 
caused by the action of the eccentric rod 
that is not supposed to be in gearing, but 
is nevertheless affecting in a marked de- 
gree the action of the eccentric rod that 



down as being among those that are past 
finding out. The effect of moving the 
point of link suspension can readily be 
seen by the most casual observation. In 
the accompanying illustration showing the 
Angus Sinclair valve model with piston 
and reverse lever in the center it will be 
seen at a glance that by moving the sus- 
pension point of the link, as can readily 
be done in the model, either forward or 
backward, the effect is to raise or lower 
the link, as the case may be, as the line 




VALVE MODEL WITH PISTON VALVE. 



s in gearing. It is usual to ascribe the 
variations in the cut-off to the angular 
advance of the main rod. This would 
doubtless be true if the eccentrics were 
set at the same point as the crank is set, 
Dut as they are set nearly at right angles 
to the crank the angular advance of the 
main rod has a corrective effect on the 
peculiarities of the link motion. 

In common practice it is not necessary 
o trouble ourselves about these involved 
problems. They may very safely be set 



of the center of suspension is not in the 
same plane as the engine frames. In fact, 
the only points where the link is in a 
perpendicular position is at the two cen- 
ters when the piston is at the extreme 
ends of the stroke. It may be noted that 
moving the saddle pin backward or for- 
ward affects the distribution of the cut-off 
and has the effect of equalizing or dis- 
torting the points of cut-off according to 
the direction in which the pin is moved, 
while moving the link saddle higher or 



25 



THE VALVE-SETTER'S GUIDE 



lower upon the link increases or dimin- 
ishes the distance of the cut-off point 
from the end of the stroke or pencilled 
mark. Indeed it may be remarked that in 
the case of a new saddle it is merely a 
matter of careful experiment which neces- 
sarily requires repetition, as the move- 
ment of the link saddle affects the valve 
opening at the extreme ends of the stroke 
so that the reverse lever should be placed 
in the end notches and the valve openings 
re-examined after each saddle experiment. 
It might be added that after the ' for- 
ward cut-off has been carefully adjusted 
it does not follow that the backward cut- 
off will be found to be correct. Other 
changes and compromises may have to be 
made, but it should be noted that if we 
have disposed of the right and left sides 
of our engine, and have the cut-off ad- 
justed, say at 6 ins. in the back and S Z A 
ins. in front, it is not necessary that the 
same figures should be established as an 
absolute necessity for the backward mo- 
tion of the engine. It is enough that the 
points are equalized to each other, and 
while the forward and backward motions 
of the engine can be equalized exactly if 
there is a new quadrant to be made it 



will be found that where the notches are 
already made in the quadrant it will be 
hardly possible to arrange the cut-off 
points so that they will exactly cor- 
respond. 

This leads us to observe that which 
will be noticed, that no matter how care- 
fully the entire valve gearing may be 
adjusted it will be found that when the 
locomotive is overhauled for general re- 
pairs variations have occurred that seem 
to the casual observer extremely puzzling. 
It is common to belittle the orignal con- 
struction and set down the apparent errors 
in organic construction to a lack of ability 
or care in the first adjustment of the 
mechanism. This is a gross injustice, and 
if we could only dimly discern the vicissi- 
tudes through which the mechanism has 
passed and measure the blows of circum- 
stance that have fallen upon the multiplex 
parts of the elastic contrivance we would 
perhaps recognize the fact that it is re- 
markable that machinery so involved and 
so subject to disturbing influences has re- 
tained such a degree of perfection as it is 
often found to possess after service so 
peculiarly exacting and so painfully 
strenuous. 



26 



THE WALSCHAERTS VALVE GEAR 



V. THE WALSCHAERTS VALVE GEAR 



In treating of valve gearing as applied 
to steam engines generally, it is presumed 
that it is scarcely necessary to dwell at 
any great length on the fact that all such 
gearing is designed with a view to admit 
steam readily to the reciprocating piston 
at a time when the steam pressure will be 
most effectual in moving the piston in the 
cylinder, which movement is readily con- 
veyed through a connecting rod attached 
to the piston at one end, and to a crank 
at the other end, thereby inducing a turn- 
ing or revolving motion to a wheel and 
axle. In the economic use of steam, and 
incidentally of fuel, it is advisable to shut 
off the supply of steam as early as possi- 
ble during the piston stroke, so that the 
steam admitted to the cylinder at a high 
degree of pressure may have an oppor- 
tunity to spend its force before being per- 
mitted to pass into the outer air. It will 
be readily understood that in a cylinder 
two feet in length, if the supply of steam 
is cut off at a point when the piston has 
only traveled six inches on its course to- 
ward the other end of the cylinder, the 
steam pressure will only amount to one- 
half of the original pressure when the pis- 
ton has traveled twelve inches, because 
the steam will then occupy twice the space, 
and so on until the piston has reached the 
end of the stroke, when the pressure will 



be four times less than when admitted. 
Other causes, which need not now be 
dwelt upon, will have reduced the pres- 
sure even more than this, so that steam 
admitted at 180 lbs. of pressure per square 
inch at the beginning of the piston stroke 
will be less than 40 lbs. per square inch 
by the time the piston stroke is completed. 
In the early days of the steam engine 
the necessity for this economical or ex- 
pansive use of steam, as it is called, was 
not so great as it is now, for the reason 
that steam was used at a much lower pres- 
scure at that time, and the loss of steam 
at the end of the piston stroke was small 
in comparison with what it is now, when 
steam is admitted during the entire length 
of the stroke. Other causes soon arose 
calling for a variable supply of steam. 
With the locomotive the difference in 
grades to be climbed and in loads to be 
hauled necessitated an increase and a 
diminution of the steam pressure, and the 
brightest minds among steam engineers 
were early at work on this important 
problem. As boiler construction improved 
and higher steam pressures became pos- 
sible, the necessity for a variable valve 
motion increased. Egide Walschaerts, a 
young Belgian engineer, was among the 
first, and perhaps the most successful, in 
solving this intricate mechanical problem. 



27 



THE VALVE-SETTER'S GUIDE 



Eccentrics were already in use for the 
simple purpose of reversing the move- 
ment of the engine. This was accom- 
plished by having two eccentrics set in 
such positions that when their rods were 
in operation on a rocker that moved the 
valve rod, one rod was adjusted so that 
it would act in advance of the main crank, 
while the other, when in operation, would 
follow the crank. One rod could be lifted 
off the rocker pin and the other one at- 
tached by a simple appliance similar to 
the lifting shaft now in use on locomo- 



eccentric or crank set at right angles to 
the main crank is the primal necessity in 
the construction of the Walschaerts gear- 
ing. It can readily be understood that a 
connecting rod attached to an eccentric 
or crank so fixed and so adjusted in point 
of length that it would reach exactly to 
the movable valve while the valve was in 
the central position would, by continuing 
the movement of the engine, continue to 
place the valve in the middle of the valve 
seat when, the piston was at the end of 
the stroke, and also move the valve to 




WALSCHAERTS 



VARIABLE EXPANSION VALVE MOTION APPLIED TO LOCOMOTIVE 
98, AT BRUSSELS, BELGIUM, SEPT. 2, 1848. 



tives, the rods being furnished with hooks 
adapted to catch the rocker pin. 

This reversing contrivance attached to 
the early locomotives is alluded to in or- 
der that the condition of the valve gearing 
at the time that Walschaerts brought his 
keen intellect and engineering skill to 
bear upon the problem may be understood. 

The valve then in use, known as the 
D-slide valve, the steam ports leading to 
the cylinder and the method of exhaust- 
ing the steam through the inner cavity 
of the valve were not in any way affected 
by the work of the young Belgian en- 
gineer. The perfect adjustment of an 



the extreme end of its stroke at the mo- 
ment that the piston w*as in the middle 
of the cylinder. 

With the piston at either of the extreme 
ends of the cylinder and the valve in the 
central position, it would be found that a 
certain portion of the valve face over- 
lapped the steam ports and it would be 
necessary to move the valve a distance 
equal to the amount of lap in order that 
the steam might be readily admitted to 
act on the piston in the early part of its 
movement towards the other end of the 
cylinder. The mechanism invented by 
Walschaerts in moving the valve the re- 



28 



THE WALSCHAERTS VALVE GEAR 



quired distance from the center at either 
end of the piston is one of the cleverest 
devices in use in steam engineering, and 
is generally looked upon as the crowning 
feature of Walschaerts' masterly inven- 
tion. It should be noted that the overlap- 
ping of the valve is an essential requisite 
in the economic use of steam. If the valve 
exactly covered the ports any movement 
of the valve would cause an immediate 
opening of one port at the instant of the 
closing of the other port. The amount of 
lap makes a period of closure of the ports 
possible, and consequently renders the 
expansive use of steam already alluded 
to a mechanical possibility. 

This moving of the slide valve toward 
the desired point is effected by the en- 
gaging of the valve rod by an intervening 
combination lever which is connected to 
the crosshead by a union link, and which 
will be fully described hereafter. The co- 
relation between the combination lever 
and a radius bar driven by an oscillating 
radial link, which is driven by the eccen- 
tric rod, becomes the determining factor 
in moving the valve from the central posi- 
tion to the point desired. 

The shortening of the valve stroke, 



making it possible to close the supply of 
steam at any desired point of the piston 
stroke is effected by the oscillating radial 
link into which the radial bar attached to 
the valve rod and cross-head is movable 
by the lifting shaft, and it will be readily 
seen that as the radial link suspended 
centrally oscillates furthest at the extreme 
ends the radial bar will travel further 
when near the extreme ends of the imk, 
and as it is made to approach the center 
the motion of the bar will be shortened. 
At the center of the link it will cease 
moving altogether, and after passing the 
center it will move in the opposite direc- 
tion, thus reversing the movement of the 
engine. The moving of the valve towards 
the opening point by the use of the cross- 
head connection, as well as the interven- 
tion of the oscillating radial link, together 
with the use of the single eccentric or 
crank, are three distinct and separate fea- 
tures of this valve gearing, and these, to- 
gether with their connections and rela- 
tion to each other, will be treated in detail 
in the forthcoming chapters describing 
the construction and adjustment of this 
steam-engine attachment, as applied to 
the locomotive. 



2Q 



THE VALVE-SETTER'S GUIDE 



VI. VARIATIONS IN FORM IN THE WALSCHAERTS 

VALVE GEAR 



It will be noted that the construc- 
tion of the Walschaerts valve gearing 
as originally applied by the inventor to 
the locomotives of the Belgian State 
railways differs somewhat in detail 
from the forms in which it is now 
made applicable to twentieth century 
locomotives. These changes do not in 
any way affect the organic principles 



being fastened to the eccentric strap, 
and the other end attached to the lower 
end of the radial link. This eccentric 
was set at right angles to the main 
driving crank, that is while the piston 
would be at the extreme back end of 
the cylinder and the main crank pin 
consequently on the back center, the 
extreme point of the eccentric would 




WALSCHAERTS' VALVE GEAR, AS APPLIED TO LOCOMOTIVES BY WILLIAM MASON. 



of the device, but are merely matters 
of convenience made to suit the in- 
creased size of the engines. Among 
the changes in form it will be observed 
that the original method of causing the 
radial link to oscillate on its central 
suspension stud was by an eccentric 
attached to the main axle to which a 
rod was attached, one end of the rod 



be on the top center, or 90 degrees 
ahead of the main crank while the en- 
gine was running forward. It must be 
borne m mind that the original in- 
vention was applied to an outside ad- 
mission D-slide valve. In the case of 
a modern locomotive equipped with an 
inside admission piston valve the ec- 
centric would be set 90 degrees behind 



30 






VARIATIONS IN FORM IN THE WALSCHAERTS VALVE GEAR 



the main crank, that is on the bottom 
center. This change of position is 
made necessary from the fact that an 
inside admission piston valve must nec- 
essarily move in the opposite direction 
from that of the ordinary outside ad- 
mission slide valve. 

In addition to the change of position 
in the eccentric there is also a change 
necessary in the relative positions of 
the radius bar and valve rod, the out- 
side admission valve requiring that the 
valve rod should be attached to the 
combination lever above the radius bar 
as in Walschaerts' original design, 
whereas with an inside admission valve, 
the valve rod attachment is made be- 
neath that of the radius bar. The 
cause and effect of this change of posi- 
tion will be fully explained hereafter, 
the present reference being merely the 
need of calling attention in a general 
way to some apparent changes in the 
construction of the valve gearing, 
which in reality are not changes at all, 
but simply varying modifications of the 
same general principles. 

With this idea in mind it will be 
readily understood that the eccentric 
fulfilled the same purpose in the orig- 
inal design as the return crank does 
that in the larger locomotives with the 
advantage that the crank being at- 
tached to the outer end of the main 
crank pin its motion can readily be 
imparted to the oscillating link by a 
rod moving in the same plane, thereby 
avoiding the necessity for extended at- 
tachments which would be necessary if 
the eccentric was attached to the main 



axle inside of the engine frames while 
the oscillating link would necessarily 
be at some distance outside of the 
frames. 

Other changes of less importance 
have occurred, among which is the 
placing of the lifting shaft above the 
frames so that the radius bar is hung 
by a short hanger or suspended by an 
adjustable sleeve, instead of being sus- 
tained by a bar from beneath which in 
the case of the modern locomotive 
would be of considerable length and 
add to the degree of unwieldiness of 
the mechanism. 

Among the first to adopt the Wal- 
schaerts valve gearing to the expand- 
ing form of the modern locomotive 
was William Mason, an American en- 
gineer. The changes in the position of 
some of the parts of the mechanism 
made by him have been closely fol- 
lowed by subsequent engineers. In his 
application of the device he not only 
made the valve rod adjustable by the 
use of threaded ends on the valve rods 
on which nuts were movable to equal- 
ize the position of the valve, but he 
also applied turn buckles to the ec- 
centric rods so that the inevitable wear 
of the return crank bearing could 
be readily rectified in case of the 
lengthening or shortening of the rod 
occasioned by the refitting of the 
brasses. 

It will be noted that in the modern 
use of the radial link there is an at- 
tachment extending beyond and under- 
neath the bottom of the link. This at- 
tachment is variable in extent, and is 



31 



THE VALVE-SETTER'S GUIDE 



adapted to form a suitable connection 
for the eccentric rod. The exact loca- 
tion of the connecting point must be 
carefully considered by the construc- 
tor on account of the relation of the 
amount of throw of the crank to the 
travel of the valve. In ordinary prac- 
tice a locomotive with a piston stroke 
of 28 ins., would have a valve stroke of 
5^4 ins., while the path of the return 
crank would describe a circle 12 ins. 
in diameter. The center of the eccen- 
tric rod attachment to the link would 
thus be describing an arc 12 ins. in 
length while the radius bar being con- 
siderably nearer the centre of the link 
would move through a smaller arc 
which continues to grow smaller if 
the radius bar is moved towards the 
centre of the link. 
In the construction of some kinds of 



locomotives there are two lifting shafts 
connected by a transmission bar. It will 
be readily found that variations of this 
kind are made necessary in order to ac- 
commodate the location of other parts of 
the engine, the additional lifting shaft not 
in any way affecting the action of the 
valve gearing. 

Such briefly are the principal changes 
in form which have occurred in Wal- 
schaerts valve gearing since its orig- 
inal introduction. These changes illus- 
trate its ready adaptability to changing 
conditions and stamp it as one of those 
few mechanical contrivances that have 
come to us as nearly perfect as any kind 
of mechanism involving the changing of 
circular motion in some parts to linear 
motion in other parts can. be expected to 
be, and not surpassed in the fine quality of 
reliability. 



32 






CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 



VII. CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 



In view of the fact that the Wal- 
schaerts valve gearing does not possess 
that flexibility of adjustment common to 
shifting link valve gearings, there is 
greater need for perfect accuracy in con- 
struction. Not only must the design be 
carefully laid out, but in fitting up the 
gearing a degree of exactness must be 
attained that approaches as nearly as pos- 
sible to perfection. As a general rule it 
is very safe to presume that the design, 
as far as the draftsman's work is con- 
cerned, is correct, but the same cannot 
always be said of the machinists' work. 
Shopmen are well aware that in the proc- 
ess of hardening the wearing parts 
of machines there is a tendency to irregu- 
larities, owing to the variations in the 
sizes of the parts. This is particularly 
true in regard to the parts where the 
greatest degree of exactness is required, 
and it should be carefully observed that 
the radial link attachment, extending as 
it does some distance beyond the link 
proper, has not moved in one direction 
or the other during the hardening proc- 
ess. The application of a turnbuckle or 
other device to the eccentric rod, although 
not now used, was a ready corrective to 
variations of this kind, but it was not a 
complete remedy, as it will be readily un- 
derstood that any variation in the paths 



described by the moving parts have some 
disturbing effect on the constructor's 
design. 

Errors of this kind are more easily de- 
tected than remedied, and it may be ac- 
cepted as a rule that organic defects in 
the construction of the Walschaerts valve 
gearing can rarely be altogether reme- 
died. It is a well-known fact among shop 
men that in the construction of locomo- 
tives there is a tendency to what may 
properly be called dramatic flourishes in 
the beginning of the building of a loco- 
motive. The frames and saddle and cyl- 
inders are bolted together with a degree 
of rapidity that fills the eye that is 
pleased with superficial appearances. The 
exact alignment of the parts, however, is 
never correct by chance. Whatever is 
correct in mechanism is always difficult 
of accomplishment, and it is time well 
spent to note that the pedestal jaws of 
the frames are not only exactly square 
to each other, but that the shoes are also 
perfectly parallel. It should not be sup- 
posed that the simple matter of adding 
or subtracting a certain quantity of met- 
al to or from the shoes will restore 
or maintain a just relation of the parts 
to each other. The least variation in the 
setting of the frames has the pernicious 
effect of throwing the bolt holes in the 



33 



THE VALVE-SETTER'S GUIDE 



frames out of position, arid braces and 
guide yokes and rocker boxes are more 
or less strangers to the truth from the 
first day of their industrial existence, and 
no amount of temporary tinkering can 
•ever bring them back to where they prop- 
erly belong. This is especially true of 
the relation of the center of the main 
driving axles to the various parts of the 
Walschaerts valve gearing, and it can- 
not be too strongly instilled into the 
minds of those who are engaged in this 
important work that every precaution 
should be taken to maintain the exact 
mathematical relation of the parts to 
which the valve gearing is attached and 
from which it derives its accuracy of 
movement. This is the highest kind of 
constructive work, and to which the work 
of the draughtsman is merely preliminary. 
It is a singular circumstance that error 
multiplies as it proceeds from point to 
point, and that which is only a small frac- 
tion at the main axle becomes a consid- 
erable quantity by the time that it has 
reached the valve opening. 

In the designing of the Walschaerts 
valve gearing the length of the piston 
stroke being given, together with the 
amount of valve travel and the extent to 
which the valve overlaps the steam ports, 
and also the amount of opening or lead 
which may be deemed necessary, the com- 
bination lever is designed in such propor- 
tion as to move the valve the exact 
amount of lap and lead away from the 
central position at the time that the pis- 
ton is at the extreme end of the stroke. 
The union link and crosshead arm are 
so constructed that the combination lever 



will be in the perpendicular position when 
the piston is in the center of the cylinder. 
The radial link is so constructed that its 
arc or curve corresponds to the circle de- 
scribed by the length of the radius bar; 
that is, measuring from the point to 
where the radius bar is attached to the 
combination lever along to the center of 
the link block. The radius bar should 
be at least eight times the length of the 
space in which the link block is designed 
to travel. The longer the radius bar is 
the more direct its thrust will be on the 
valve rod, and consequently less subject 
to the disturbing and distorting effect of 
a short angular movement. The length 
of the link is such as when oscillated by 
the eccentric rod the radius bar will 
move the slide valve the desired amount 
of travel ; that is, when the link block 
which is attached to the radius bar and 
moves freely in the link is at either end 
of the link. 

As we have already stated in the case 
of engines equipped with the ordinary 
slide valve or with outside admission pis- 
ton valves, the radius bar is connected 
to the combination lever below the valve 
stem, and in the case of piston valves 
where the steam is admitted from the in- 
ner edge of the valve, called inside ad- 
mission, the connection of the radius bar 
is above the valve stem. It should be 
noted that in order to maintain the per- 
fect equality of the valve travel both in 
the forward and backward motions the 
sr-^oension point of the link should be in 
line with a point between the combina- 
tion lever's connection with the radius bar 
and valve rod, the line being drawn 



34 



CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 



parallel with the valve rod. The same 
alignment should be maintained as nearly 
as possible in regard to the eccentric rod 
and the center of the driving axle. The 
point of connection of the eccentric rod 
with the link should be parallel with the 
axle centers. In the construction of some 
classed of locomotives, especially with 
the largest kind of cylinders, the perfect 



lever, which being attached to the cross- 
head, maintains the position of the valve 
with a degree of accuracy rarely equalled 
by any kind of mechanism where circular 
motion is changed to linear or recipro- 
cating motion. 

A working model of the Walschaerts 
valve gearing is a good aid to a clear 
understanding of the mechanism, and 




FIG. i. FORWARD GEAR, LINK-BLOCK AT BOTTOM OF LINK. 



alignment of these points would necessi- 
tate an extra extension of the link arm, 
which in turn would require an excessive 
amount of eccentric throw, and hence the 
point of eccentric rod connection with the 
link arm is often at some distance above 
the centre line. The distorting influence 
of these variations is reduced to a mini- 
mum by the action of the combination 



readily reveals not only its essential fea- 
tures and advantages, but shows at a 
glance some of the seeming contradic- 
tions to other valve gearings that its ac- 
tions exhibit. Thus, in Fig. i an illustra- 
tion of the model before us, it will be 
rioted that in the forward motion the link 
block is in the bottom of the link. This 
is opposite to what occurs in the Stephen- 



35 



THE VALVE-SETTER'S GUIDE 



son shifting link, but it will be observed 
at once that it is the link block and at- 
tached radius rod that moves, and the 
action is direct and simple in comparison 
with a floating link passing through a 
variable arc, disturbing the exact position 
of the valve as it passes from point to 
point. It may be stated here that in 
Walschaerts' valve gear in the position 
shown in Fig. i the reverse lever may be 
moved from one end of the sector or 
quadrant to the other end without dis- 
turbing the position of the valve. If the 
eccentric rod is of the proper length it 
will be readily proved at either end of 
the piston stroke by moving the reverse 
lever and thereby moving the link block 
in the link. If the valve remains station- 
ary the rod referred to is of the correct 
length. If the piston is at the extreme 
front end of the cylinder and the valve 
moves forward as the link block rises in 
the link the eccentric rod is too short. If 
on the other hand the valve moves back- 
ward the eccentric rod is too long. The 
eccentric rod controls the position and 
motion of the link, and should be so 
adjusted in point of length that the 
link block and accompanying radius bar 
should not disturb the valve when the 
piston is at the extreme end of the 
stroke. 

A peculiarity of the gearing may be 
noted at this point which affects the 
movement of the valve advantageously. 
As shown in Fig. i, the eccentric rod is 
on the bottom center, and when in motion 
moves the link at a comparatively high 
rate of speed, the motion of the link be- 
ing reduced to a minimum as the eccen- 



tric rod passes around what are prop- 
erly called the dead centers in its cir- 
cular path. It will thus be seen that at 
the moment when the eccentric or return 
crank is at the lowest or highest point 
of its path the valve, having its motion 
conveyed to it by the oscillating link, is 
traveling at its highest velocity. This is 
at the exact point where the opening of 
the valve occurs, and coincident with the 
rapid movement induced by the location 
of the eccentric or return crank the veloc- 
ity of the valve travel is further induced 
by the action of the combination lever, 
which, acting on the radius bar connec- 
tion as a fulcrum, has moved the valve 
in its path the increased distance required 
to overcome the space occupied by the 
lap and lead. The opening of the valve, 
therefore, occurs more rapidly on account 
of the movement of the combination 
lever, and if we follow the movement 
until the middle of the piston stroke has 
been reached it will be found that there 
is a diminution of speed not only on ac- 
count of the return crank passing the 
dead center, but this pause in the valve's 
motion is further accentuated by the com- 
bination lever passing the vertical dead 
center of its connection to the radius bar 
and valve rod. This double eccentricity, 
as has been stated, emphasizes the rapid 
opening and closing of the steam ports 
and prolongs the period of full opening. 
These features are of decided advantage 
in any kind of valve gearing used in steam 
engines. 

In overcoming defects in construction 
the eccentric rod is usually the part in 
which any change is made. This rod may 



36 



CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 



be lengthened or shortened to correct er- 
rors in the location of the main axle 
center or link center. The central po- 
sition of the valve or the exact amount 
of opening of the steam port at each end 
of the piston stroke can readily be ad- 
justed by lengthening or shortening the 
valve rod, which is usually fitted with ad- 
justable threaded nuts. It may be added 
that the slightest variation of the return 
crank from its proper position at right 
angles to the main crank will be readily 
discovered by comparing the action of 
the valve as shown in the forward move- 
ment of the engine with the action and 



position of the valve in the backward 
movement. Referring again to Fig. I, it 
will be readily recognized that in the event 
of the valve showing a greater amount 
of opening in the forward motion than in 
the backward motion the variation may 
be divided by moving the return crank 
connection the required amount nearer to 
the main crank, or by moving the point 
of suspension of the link nearer to the 
valve; both of these organic changes hav- 
ing the same effect, neither of these 
changes should be made except under 
very pressing conditions, and after re- 
peated experiment and identical results. 



37 



THE VALVE-SETTER'S GUIDE 



VIII. ADJUSTING THE WALSCHAERTS VALVE GEAR 



The operation of adjusting or setting 
the valves, as it is called, may be most 
readily begun by connecting all the levers 
and rods with the exception of the eccen- 
tric rod which connects the crank pin to 
the link arm. This admits of the valve 
being moved backward or forward in or- 
der to obtain the markings on the valve 
rod showing the exact points of the valve 
opening. These markings on the valve rod 
as well as the markings in the rims of 
the driving wheels showing the dead cen- 
ters or points where the piston is at the 
extreme ends of the stroke, are made in 
the same manner as the markings on loco- 
motives equipped with the Stephenson 
shifting link. The same trams may not 
suit in both cases as the guide yokes or 
bearings or other fixed parts upon which 
a tram may be steadily held vary in their 
positions according to the location of the 
parts, but the dimensions and form of a 
suitable tram will readily suggest itself 
to an intelligent mechanic. A fine centre 
punch mark should be made on the valve 
rod at the exact points where the port 
edges of the valve are exactly square with 
the admission port edges of the valve seat. 

The eccentric rods may then be con- 
nected and the work of moving the driving 
wheels may be begun. Assuming that the 
reverse lever is at the extreme end of the 



quadrant in the forward motion, it will 
be readily seen whether the valve rod is 
of the proper length, as soon as the two 
valve rod markings are made when the 
main rod has reached the dead centres. 
Whatever variation there may be can 
readily be rectified by dividing the ap- 
parent variation by the adjustable nuts 
usually atached to the valve rod. When 
the forward motion has been corrected in 
this manner, suppose the markings on the 
valve rod should be as shown in Fig. 2, 
it will readily be seen, apart from the 
variation observable in the markings in the 
back motion, that the opening of the 
valve has to be increased in the case of 
the forward motion, and diminished in the 
back motion. Now assuming that the 
change is to be made on the left side of 
the engine and that the main rod is on 
the forward dead center as in Fig. 1, it 
will be readily observed that in order to 
increase the opening of the valve it must 
be moved backwards toward the link. 
To accomplish this movement the eccentric 
rod must be shortened, and if it were con- 
venient to remove the pin connecting the 
forward end of the eccentric rod from the 
link arm, allowing the rod to remain in 
position, and moving the valve the re- 
quired distance it would be seen by the 
variation in the edges of the hole in the 



38 



ADJUSTING THE WALSCHAERTS VALVE GEAR 



link arm from that of the eccentric rod 
how much the eccentric rod would require 
to be shortened. This method, however, is 
not entirely to be depended upon, as there 
is a certain amount of lost motion both 
in the valve and radius rod connections, 
as well as on the central pivot upon which 
the link is suspended. These, in addition 
to the link block would admit of a slight 
motion backward or forward of the ex- 
treme point of the link arm without show- 
ing any motion of the valve. Generally 
speaking the eccentric will require to be 
moved or shortened as in the present case 
between two and three times more than 
the amount required in the opening of 
the valve. The exact ratio can be deter- 
mined by measuring the distance' from 
the central stud upon which the link oscil- 
lates to the center of the link block, and 
supposing this distance to be 8 ins., then 
measuring the distance from the central 
stud to the center of the link arm con- 
nection with the eccentric rod, and sup- 
posing that to be 20 ins., it will thus be 
seen that the eccentric rod must be moved 
two and a half times the amount that we 
desire to move the valve or increase the 
opening. So if the increase desired, as in 
the present instance, should be one-six- 
teenth, it will require a shortening of the 
eccentric rod amounting to five-thirty-sec- 
onds of an inch. 

It may be stated at this point that there 
is no need of experimenting with the union 
link. It might be imagined at first glance 
that by lengthening the union link the 
opening of the valve could be increased. 
Any change made in this lever, however, 
with a view to open the valve at one end 



of the piston stroke, would have the effect 
of closing the valve a corresponding 
amount at the other end of the stroke. 
After rectifying the variation as shown 
in Fig. 2, as nearly as possible, by shorten- 
ing the eccentric rod, it may be found 
that there is still a slight variation be- 
tween the amounts of openings. This is 
proof of a slight organic defect probably 
in the position of the eccentric or return 
crank, and if the defect does not exceed 
one thirty-second it is as well to adjust 
the forward motion as nearly correct as 
possible and allow whatever variation 
there may be to remain with the backward 



B 



A 



2H 



1 



FIG. 2. FORWARD MOTION F; BACK- 
WARD B. 

motion of the engine, which as a rule, is 
not so frequently in use as the forward 
motion. 

In the case of adjusting the valve gear- 
ing of a locomotive equipped with the 
Stephenson shifting link, it is possible un- 
der any condition to arrange the eccen- 
trics and eccentric rods to bring about an 
exact opening of the valve at the desired 
point of the piston stroke on either the 
forward or backward motion of the engine. 
On an engine equipped with the Wal- 
schaerts valve gear this is not always the 
case, but unless the organic defect in the 
Walschaerts valve gearing is of a serious 
kind, the gearing may be adjusted so 



39 



THE VALVE-SETTER'S GUIDE 



nearly correct that it will likely be in 
much better condition during its period of 
service than the shifting link gearing will 
be after a few weeks' service. In any 
kind of valve gearing it is well that the 
point at which the engine will likely do the 
greatest amount of work, should be most 
carefully adjusted. In passenger locomo- 
tives this point is usually with the valve 
cutting off the supply of steam at some 
point considerably less than the full stroke. 
It will generally be found that in the case 
of the Walschaerts gearing the cut-off 
point will be nearly correct. In the event 
of the variation from the exact clos- 






1/6 



32 



'6 



FIG. 3. B, BACK; F, FORWARD. 

ing of the valve at each end of the piston 
showing a more continued opening at the 
front end, thereby admitting steam a 
longer period of time, the valve rod may 
be slightly changed by the adjustable nuts, 
as it is more desirable to have a slightly 
prolonged opening in the back of the pis- 
ton to make up for the space occupied by 
the piston rod. 

Turning our attention to the right side 
of the locomotive and proceeding by the 
same method to mark the valve rod when 
the crosshead is at the dead centers on the 
forward and backward motions, we shall 
presume that the markings are found to 
be as shown on Fig. 3; it will be ob- 



served that the valve shows an opening of 
five-sixteenths on the forward motion, 
while the valve is lapping one thirty-second 
on the backward motion. We shall as- 
sume that the central position of the valve 
on both motions is nearly correct. The 
position of the link when the main crank is 
on the dead centers should be carefully 
noted, and if the link retains its exact po- 
sition when the engine is on either centres, 
the eccentric crank position may be as- 
sumed to be correct. If a variation of the 
position of the link is observed, it is safe 
to assume that there is an error in the 
position of the crank. Placing the engine 
on the back centre as in Fig. 4, it will be 
readily seen that the valve must be moved 
forward in order to obtain the desired 
amount of opening. As the eccentric rod 
is now acting indirectly on the valve rod, 
the eccentric rod must be moved in 
the opposite direction, and hence the 
crank connection must be moved a 
sufficient distance backward or toward the 
main crank to effect the required change. 
The exact amount may be ascertained by 
the same process as used in shortening the 
eccentric rod on the left side of the en- 
gine. As the changing of the position is 
a matter of some difficulty involving the 
fiting of a new key to hold the eccentric 
crank in place, it is well to secure the 
crank temporarily in place and move the 
engine from centre to centre to ascertain 
if the desired effect has been obtained. 
A change of the position of the eccentric 
crank may involve a slight change in the 
length of the eccentric rod, and even with 
the most careful adjustment it is rare in- 
deed to secure the perfect coincident 



40 



ADJUSTING THE WALSCHAERTS VALVE GEAR 



amount of valve opening at each of the 
four points of admission, and also to ar- 
range the points of cut-off so that the 
steam pressure may be most advantageous- 
ly used in meeting the various require- 
ments of locomotive service. 

It may be added that the amount of 
clearance between the link block and link 
at the extreme ends of the travel of the 



lengthening or shortening the radius rod, 
but as the length of this rod should co- 
incide exactly with the arc of the link it is 
not good practice to change the length of 
this rod ; that is, if its length be correct. 
In closing it is well to remember that 
when locomotive boilers are filled, and all 
the parts of the engine more or less heated, 
there is a tendency to slightly distort the 




FIG. 4. WALSCHAERTS VALVE GEAR IN BACK MOTION. 



block should be carefully noted. It is 
usual to allow a greater amount of clear- 
ance at the bottom of the link as the 
tendency of the link block is to approach 
nearer the bottom of the link as the parts 
wear. Any marked deviation from an 
equable centre affects the travel of the 
valve. Slight variations in the amount of 
valve opening may also be remedied by 



operations of the valve gearing and it is 
well that the skilled mechanic should take 
an opportunity to observe the changes if 
any, as such tendencies are very often in 
the direction of magnifying any slight 
shortcoming from the exact points to be 
desired, and a final skillful change may be 
made that may make a nearer approach to 
perfection. 



41 



THE VALVE-SETTER'S GUID] 



IX. THE BAKER-PILLIOD VALVE GEAR 



The twentieth century locomotives have 
grown to such colossal proportions that 
the arrangement of the valve gearing 
outside of the frames has become a 
primal necessity. The limited space be- 
tween the frames with the incre'asing 
size of axles and eccentrics renders it 
particularly difficult to adjust and ex- 
amine the Stephenson shifting link gear 
under such conditions and doubtless this 
was the chief cause that called the Wal- 
schaerts valve gearing into prominent use 
in American locomotive service. As we 
have endeavored to show in the pre- 
ceding chapters the Walschaerts gearing 



has several advantages over that of the 
shifting link. It also has its drawbacks, 
which in these days of rapid construction 
and hard usage are not far to seek. It 
is not to be wondered at therefore that in 
the atmosphere of American enterprise 
many clever mechanicians have been at 
work devising means of actuating and 
controlling the valve gear of the modern 
locomotive. Perhaps the most successful 
attempt in the present century in this 
direction has been the combination known 
as the Baker-Pilliod valve gear. The de- 
vice resembles the Walschaerts gearing 
in several features. It has the eccentric 




THE BAKER-PILLIOD VALVE 'GEAR. 
42 



THE BAKER-PILLIOD VALVE GEAR 



crank attached to the main crank pin, 
and a combination lever deriving its mo- 
tion from the crosshead. With these two 
factors in the motion the resemblance 
ceases, the chief variation being the ab- 
sence of the radial link. As is well 
known the movement of a radial link 
whether shifting or fixed is a source of 
error in all motions. These errors are 
caused by the slipping of the link-block 
and are especially marked in the case of 
the shifting link as it travels through a 
longer arc than is usual in the case of 
links oscillating upon a fixed center. 

In view of this fact, it will be readily 
understood that if the motion of a slid- 
ing valve can be perfectly controlled and 



the length of stroke varied without the 
intervention of a radial link, a real gain 
in the economical use of steam will be 
made. The best proof of this is shown in 
the use of the Corliss valve on stationary 
engines. This kind of valve gearing with 
its delicate governor and complex mech- 
anism is not suited for the incessant vi- 
brations and distorting strains of loco- 
motive service. The ideal valve gearing 
for a locomotive must have the element 
of rigidity in a marked degree, and at the 
same time possess that flexibility of 
adaptation essential to the various re- 
quirements of the service. The best use 
of steam pressure is possible only when 
under perfect control. 



43 



THE VALVE-SETTER'S GUIDE 



X. CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 



Coming to the valve gearing under 
consideration it will be observed that 
there are a number of rods in addition 
to those we have alluded to, besides lev- 
ers and bell cranks and brackets which 
in appearance form a complex combina- 
tion, but which when followed one by 



gree of rapidity toward the center and 
diminishes in velocity toward the ends of 
its stroke. The same irregular linear 
movement is made by the eccentric rod, 
and in Fig. i it will be seen that the 
crosshead is near the center of its stroke, 
the swiftest part of its motion, while the 




FIG. i. OUTLINE OF BAKER-PILLIOD VALVE GEAR. 



one lead from the circular movement of 
the eccentric crank and the reciprocating 
movement of the crosshead to the sim- 
ple reciprocating motion imparted to the 
valve rod. It will be readily understood 
that neither of these primary movements 
are regular in their linear velocity, the 
crosshead travels with an increasing de- 



eccentric crank which is set at right 
angles to the main crank is experiencing 
its slowest movement. The union link 
attached to the crosshead and the eccen- 
tric rod are attached to the separate ends 
of a bell crank. The end of the bell 
crank attached to the eccentric rod de- 
scribes a circle or ellipse, according to 



44 



CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 



the relative proportions of the arms of 
the bell crank, but always at irregular 
velocity. This varying motion is con- 
veyed by a coupling and hanger to an- 
other bell crank, the lower end of which 
is attached to the valve rod, which in 
turn is attached to the valve rod cross- 
head to which the valve stem is attached 

REACH ROD 



REVERSING 
SHAFT 



increasing rapidity and closes with a 
speed equal to that of the piston. 

In regard to the reversing gear it may 
be shown more clearly by referring to 
Fig. 2, which represents a skeleton sketch 
of the Baker-Pilliod valve gear, shaded, 
and which we have purposely distorted 
to show more clearly the movable and 
fixed parts of the gearing. It will be ob- 
served that the continuance of the ec- 
centric arm after passing the two bell 




CROSSHEAD CONNECTION 



FIG. 2. PURPOSELY DISTORTED SKELETON SKETCH OF GEAR. 



and held in place by adjustable nuts. The 
result of the two initial motions con- 
veyed through this double system of bell 
cranks is such that the valve travels as 
fast as the piston at the beginning of its 
stroke and by the time that the piston has 
moved about one-twentieth of its stroke 
the valve is wide open and the valve then 
moves very slowly during the period 
while the piston is traveling with increas- 
ing rapidity during the first half of its 
stroke. As the piston approaches the 
release point the valve again travels with 



cranks already described is attached to 
a hanger G, at the point F. This hanger 
is suspended from the upper end of a 
radius yoke J, which is attached to a 
fixed point at K. The point F therefore 
swings about the point H. This radius 
yoke J is suitably attached to the gear 
reach rod which is connected to the re- 
versing shaft. Assuming that the piston 
and slide valve and reverse lever are all 
in the central position, it can be seen 
that in the event of the reach rod being 
moved to the front end of the quadrant, 



45 



THE VALVE-SETTER'S GUIDE 



the lower arm of the reversing shaft will 
be drawn backward, carrying w T ith it the 
radius yoke, which hangs from the top of 
the reverse yoke. This backward move- 
ment of the radius yoke has the effect of 
lowering the hanger G, so that the point 
F will be considerably lowered, carrying 
with it the point N of the second cell 
crank and consequently drawing the valve 
rod backward and opening the front 
steam port. 

If on the other hand the reverse lever 
is drawn backward to the back end of the 
quadrant the radius yoke will be moved 
forward, carrying with it the hanger G, 
and raising the point F, the effect being 
to raise the bell crank at N, which 
moves on the fixed point P. Thus the 
lower part of the bell crank at Q will be 
moved forward, carrying with it the valve 
rod and opening the back steam port in 
the cylinder, thereby inducing a back- 
ward motion of the engine. This de- 
scription presumes an outside admission 
valve with the main rod at the lower or 
bottom center. 

Having thus shown the action of the 
radius yoke on the second bell crank and 
its effect on the valve rod, it can be 
readily imagined that the placing of the 
reversing lever at any of the intervening 
spaces between the center of a quad- 
rant and its extreme ends, have their 
relative effect on the position of the bell 
crank and the corresponding effect on 
the motion of the valve rod. 

It will thus be seen that there are a 
large number of joints through which the 
motion must necessarily pass from the 



main crank pin and crosshead connection 
before the movement reaches the slide 
valve. This is one of the drawbacks in 
the Stephenson shifting link, and it is one 
of the chief merits of the Walschaerts 
valve gearing that the crosshead connec- 
tion is immediately attached with only 
one joint between the combination lever 
and valve stem. There is this particular 
advantage, however, in the Baker-Pilliod 
gear, that the parts lend themselves read- 
ily to massiveness and rigidity of con- 
struction which is impossible in the case 
of the Stephenson shifting link gear and 
is only partially so in the case of the 
Walschaerts gearing. 

The diagram Fig. 3 shows the shape 
of the distorted elliptical path of point 
L, and the portions of the ellipse passed 
over by the point L for port openings 
and for lap and lead. The same letters 
that are used in Fig. 2 are used in Fig. 
3. The ellipse marked Y is the path fol- 
lowed by point L when in forward gear, 
and the ellipse X is that followed in 
backward gear. The curves in Fig. 3 
marked 1, 1, is that followed by the point 
F in full forward gear, the curve 2, 2 is 
that followed when the reverse lever is 
in the center, and curve 3, 3 is that for 
full backward gear. 

It may be added that the lead or open- 
ing of the valve at the end of the piston 
stroke is an unvarying or constant quan- 
tity, so that the length of the valve stroke 
or point of cut-off of steam supply does 
not in any way affect the exact amount of 
opening at the beginning of each piston 
stroke, while the degree of rapidity with 



46 



CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 




FIG. 3. DIAGRAM OF MOVEMENTS OF PARTS OF BAKER-PILLIOD GEAR, 

which the valve opens during the early sired point of cut-off is not surpassed by 
part of the piston stroke or the rapidity any kind of valve gearing applied to lo- 
with which the valve closes at the de- comotives. 



47 



THE VALVE-SETTER'S GUIDE 



XL ADJUSTING THE BAKER-PILLIOD VALVE GEAR 



In the adjustment of the gearing it may 
be noted that it is essential that the pro- 
portions of the various parts be correctly 
designed by following a precise formula, 
aided, if possible, by an adjustable model. 
The setting of the valves, in the same 
sense of the words as is used in the care 
of the Stephenson gearing, would be an 
idle experiment. This is one of the 
advantages of the Baker-Pilliod gearing 
that when properly constructed and ad- 
justed to the locomotive the valve gearing 
passes outside of the pale of the con- 
stant consideration of the engineer or 
mechanic, and while liable, of course, to 
a certain amount of wear and possible 
fracture, it is not subject to those erratic 
variations so peculiar to some forms of 
valve gearing. Generally speaking, the 
eccentric rod is the only part that may 
occasion a renewal of adjustment, as the 
wear of the bearings at the main crank or 
in the main driving boxes may occasion 
a slight variation in point of length of 
the eccentric rod. The gear reach rod 
and eccentric arm as well as the valve 
rod are all fitted with means for adjust- 
ment in regard to length, so that the 
equalization of the travel of the valve 
can be readily effected in the original as- 
sembling of the parts. 

The amount of lead or opening of the 



valve at the beginning of the piston stroke 
can be increased or diminished by 
lengthening or shortening the lower arm 
of the bell crank. It can be readily seen 
that by lengthening the arm of the bell 
crank attached to the valve rod connection 
that an increase in the length of the 
valve stroke will be made, and this in- 
crease will be added to the amount of 
valve opening at the end of the piston 
stroke. A corresponding decrease will 
occur in the case of shortening the bell 
crank arm. These organic changes are 
rarely necessary, and it is questionable 
whether in the instance of a change in 
the amount of valve opening being neces- 
sary it would not be advisable to make 
a slight change in the length of the com- 
bination lever. It will be readily noted 
that by shortening or lengthening that 
lever the stroke of the valve would be af- 
fected in a lesser degree. 

The exact position of the eccentric crank 
in relation to the main crank is a vari- 
able point to the designer, and is adapted 
by him to suit the requirements of the 
valve gear construction. In the case of 
an inside admission valve, the return or 
eccentric crank follows the main crank 
when the engine is running forward. In 
the case of an outside admission valve, 
the eccentric crank is set a corresponding 



48 



ADJUSTING THE BAKER-PILLIOD VALVE GEAR 



distance ahead of the main crank. The 
length of the eccentric crank is also a 
variable quantity to the designer. The 
eccentric crank used in the case of an 
inside admission valve being longer than 
that used in the case of an engine equipped 
with a valve having outside admission. 
The necessity for this variation is appa- 
rent when it is observed that the angle 
of inclination of the eccentric rod is an 
ascending one towards the lifter bar and 
bell crank. These necessary variations 



of hardened pins and bushings affords an 
opportunity of retaining the action of the 
gearing with a degree ^of accuracy which 
leaves little or nothing to be desired in 
the ready application of means for the 
maintenance of the wearing parts. This 
is a marked advance over the use of slid- 
ing blocks and cumbrous rockers which 
cannot be overestimated and reflects much 
credit on the practical ingenuity of the 
accomplished inventors. 
It need hardly be stated lhat the gear- 




FIG. i. BAKER-PILLIOD VALVE GEAR ARRANGED FOR INSIDE ADMISSION. 



will be readily observed in comparing the 
illustration of the different positions of 
the eccentric crank, as shown in Fig. i, 
which displays the arrangement of the 
eccentric crank and lifter bar adapted 
to an inside, admission valve, with that 
of Fig. 4, which shows the parts arranged 
from an outside admission valve. 

An admirable feature of the gearing 
is the fact that all the connections are 
mechanically positive and the exchange 



ing is capable of many changes in organic 
structure and is readily adaptable to any 
length of valve stroke. In its present 
form as applied to a large number of 
American locomotives the throw of the 
eccentric crank is such as describes a cir- 
cle of seven inches in diameter producing 
a valve travel when in full gear of six 
inches. This could be easily increased 
or diminished to suit the requirements of 
any size or design of locomotive. The 



49 



THE VALVE-SETTER'S GUIDE 



equable motion of the eccentric rod trav- 
eling as it does in parallel precludes the 
•possibility of any of that peculiar varia- 
tion in motion incident to all movements 
where circular motion is changed into 
linear motion and which is such a disturb- 
ing factor in the action of the Stephenson 



7?e*e/ Toe? 



and which prevents the 'motion of the 
valve gearing from having a distorting ef- 
fect on the frames, and adds much to their 
necessary rigidity. 

In brief assuming that the design of the 
valve gearing is correct, the adjustment 
of the parts is a matter comparatively 




FIG. 4. BAKER-PILLIOD VALVE GEAR ARRANGED FOR OUTSIDE ADMISSION. 



shifting link motion, and is not alto- 
gether absent in the Walschaerts valve 
gearing. This regularity of movement is 
fully and completely secured by the car- 
riage of the gearing, which is almost en- 
tirely supported in a substantial, chan- 
neled cradle set between the guide yoke 
and a cross tie extending over the frames, 



easy of accomplishment, while the com- 
pleted, clever contrivance, when once ad- 
justed, has the rare quality of retaining 
that degree of accuracy which approaches 
as near to perfection as can be expected 
in the strenuous segregation of diverse 
forces that have their being in locomotive 
service. 



/ 



50 



THE JOY VALVE GEAR 



XII. THE JOY VALVE GEAR 



In Dr. Angus Sinclair's monumental 
work "Development of the Locomotive 
Engine," there are about fifty different 
types of locomotive valve gearing de- 
scribed and illustrated, and, while many 
of these are merely variations of two 
distinct types, all of them bear evidences 
of a high order of mechanical ingenuity, 
and it would seem as if the problem of 
steam distribution is one that has engaged 
the attention of the brightest minds in 
the realm of steam engineering and that 
the complete solution of the problem, like 
the squaring of the circle, is one that 
eludes and ever will elude the seeker 
after perfection. Even the survival of 
the fittest is often hindered by ignorance 
and prejudice, and it is marvelous with 
what tenacity the mechanical mind will 
cleave to established institutions. It may 
be remarked that the most successful in- 
ventions and variations in locomotive 
engine valve gearing have been made by 
skilled mechanicians whose experience in 
actual work has sharpened their intellects 
and in many cases rendered the applica- 
tion of their theories comparatively easy 
by giving an opportunity in the locations 
where they were employed to test the 
merits of their devices. 

David Joy, an English locomotive 
superintendent, patented a valve motion 



in 1879. Although belonging to the radial 
gear variety of valve motions, it has sev- 
eral features distinctively its own. It 
has neither eccentric nor crank, the valve 
deriving its movement from a system of 
levers connected with the main rod and 
varied by the application of a sliding 
link. 

The motion for the valve is taken di- 
rectly from the connecting rod and by 
utilizing independently the backward and 
forward action of the rod, due to the 
reciprocating motion of the piston, and 
combining this with the vibrating action 
of the rod up and down, a movement re- 
sults which is used to actuate the valves 
of engines having any combination of lap 
and lead, and giving an almost mathe- 
matically correct cut-off for both sides of 
the piston for forward and backward mo- 
tion, and for all points of expansion in- 
termediately. The action of the gear may 
be understood by reference to the engrav- 
ings, Figs. 1, 2, 3 and 4, which are respec- 
tively an elevation, plan, a transverse 
section on XY of Fig. 1 looking forward, 
and modified arrangement of the gear. 

From a point, A, Fig. 1, in the con- 
necting rod, motion is imparted to a 
vibrating link, B, constrained at its lower 
end, H, to move vertically by the radius 
rod, C, which is pivoted at I. From a 



Si 



THE VALVE-SETTER'S GUIDE 



point, D, on this vibrating link, B, hori- 
zontal motion is communicated to the 
lower end of a lever, E, from the upper 
end of which lever the motion is trans- 
mitted to the valve spindle by the rod- G. 
The center or fulcrum, F, of the lever E, 
partakes also of the vertical movement of 
the connecting rod to an extent equal to 
the amount of its vibration at the point 
A; the center F is for this purpose car- 



crum, F, of the lever, E, is represented in 
Fig. i. The shaft, L, and the links can 
be partially rotated on the center of the 
former, so that the slots in the links will 
be inclined over to either side of a verti- 
cal position, as shown at W and X. This 
is done by means of an ordinary reverse 
lever connected to the upper arm, M, 
attached to the shaft, L. When the links 
are thus inclined, the vertical movement 




FIG. i. ELEVATION OF JOY'S VALVE GEAR. 



ried vertically in blocks which slide in 
slots in the links JK, which are curved to 
a radius equal to the length of the rod G, 
connecting the lever F to the valve 
spindle. These links are attached to a 
shaft, L, Figs. 2 and 3, corresponding to 
the ordinary lifting shaft of a link mo- 
tion. The center of this shaft corre- 
sponds to the position in which the ful- 



of the lever, E, causes the blocks in the 
links and the center, F, to traverse a path 
inclined to a vertical center line; and to 
diverge from it to either side. The 
center, F, therefore, has a horizontal 
movement, the extent of which depends 
upon the degree of inclination of the 
links, and the direction of whicji is gor- 
erned by their position. 



52 



THE JOY VALVE GEAR 



The forward or backward motion of 
the engine is governed by giving the slots 
this inclined position on one or other 
side of the vertical center line; and the 
amount of expansion depends on the 
amount of the inclination, the exactly 
central or vertical position being "mid- 
gear." In that position steam is admitted 
at each end of the stroke to the amount 
only of the lead; and this is done exactly 
equally on each side of the center line, 
the amount of lead being constant for 
forward and backward motion, and for 
all degrees of expansion. Thus when the 
crank is set at the end of the stroke 



described by the lower end, D, of the 
lever, E, and this would give an unequal 
port and unequal cut-off for the two ends 
of the stroke. But this error is corrected 
by attaching the lower end, D, of the 
lever, E, to the vibrating link, B; for 
while the point A in the connecting rod 
is performing a nearly true ellipse, the 
point D in the vibrating link B is moving 
in a figure, DOPQ, Fig. i, like an ellipse 
bulged out on the lower side, and this 
irregularity is so set as to be equal in 
amount to the versed-sine of the arc 
described by the lower end, D, of the 
lever, E, thus correcting the above error, 




FIG. 2. PLAN OF THE JOY VALVE GEAR. 



either way, the center, F, of the valve 
lever coincides with the center of the slot, 
and, therefore, the slot may be moved 
over from forward to backward gear 
without affecting the valve at all. 

It will be seen at a glance that if the 
lower end, D, of the lever, E, were at- 
tached directly to the point, A, on the 
connecting rod, it would travel in the 
path of the ellipse, AN, represented by 
dotted lines, and there would be imparted 
to the center, F, of that lever, an unequal 
vibration above and below the center of 
the links, JK. The extent of inequality 
would be twice the versed-sine of the arc 



and giving an equal travel to the center, 
F, of the lever above and below the cen- 
ter of the slot. At the same time the 
error introduced by the movement of the 
end of the valve-rod, G, is corrected by 
curving the slots or links, JK, to a radius 
equal to the length of G. 

Referring again to the equalizing of the 
traverse of the center, F, of the lever, 
E, in the slot, JK, the unequal traverse 
may be either under corrected or over 
corrected by shifting the point D in the 
vibrating link, B, near to or further from 
A ; by this means a later point of cut-off 
may be given to either end of the cylinder 



53 



THE VALVE-SETTER'S GUIDE 



at will, and the engine may thus have 
more steam admitted to one side of the 
piston than to the other, if required. The 
same thing may be done for the lead. By 
altering the position of the crank for 
which the lever center, F, coincides with 
the center of the slots, JK, an increased 
or diminished lead may be given. The 
central positions and exact connections 




FIG. 3. SECTION OF GEAR. 

are, however, in all cases standard and 
equal. 

Hitherto the center, F, of the lever, E, 
which gives motion to the valve spindle, 
has been described as carried in curved 
slots. This plan is given as the most 
simple to manufacture, but if preferred 
the center, F, may be carried by a radius 
rod so that its vibration will make the 
center, F, of the lever, E, describe identi- 
cally the same arc as if moving in the 
slots JK. 



In locomotives with small wheels the 
link, C, may come so low down as to be 
in danger of being knocked off. For such 
cases, and for others when it may be 
considered desirable, Mr. Joy proposed 
the plan shown in Fig. 4, in which the 
link, B, is cut off at the center, D, and is 
connected at that point by a rod, S, to a 
crank, T, on the end of the crankpin. The 
movement of the valve produced by this 
mechanism is almost identical with the 
other. 

The Joy valve gearing has met with 
considerable favor on a few of the British 
railways, notably on the Great Western 
Railway of England. This railroad, con- 
structed by the justly celebrated engineer, 
Brunei, is among the best built and main- 
tained railways in the world. The long, 
straight stretches of flat lands over which 
most of the road passes form an excellent 
opportunity for fine roadbeds, and conse- 
quently the locomotives are comparatively 
free from those vibratory oscillations 
which are a severe test on the rigidity of 
almost all forms of valve gearing. It 
will be readily observed that any vertical 
disturbance on the main rods of locomo- 
tives equipped with the Joy valve gear 
would have a particularly distorting effect 
on the gearing, and this is the cause of 
the very limited use to which the gearing 
has been put on American railroads. As 
roadbeds improve, the gearing may come 
into more popular favor. It unquestion- 
ably takes its place among the leading 
devices used in steam distribution. Like 
the Corliss valve gearing and others of 
real merit, the Joy valve gearing has 



54 



THE JOY VALVE GEAR 

advantages peculiarly its own, but its conditions which we are not likely to 
best work can only be done under reach for many years to come. 




~t~ 



FIG. 4. JOY'S GEAR MODIFIED SO AS TO RAISE PARTS FROM TRACK. 



55 



THE VALVE-SETTER'S GUIDE 



NOTE ON SETTING THE SLIDE VALVE OF A STATIONARY 

ENGINE 



The valve rod connections being prop- 
erly adjusted, place the crank on the 
dead center and move the eccentric around 
on the axle, in the direction in which the 
engine is intended to run, until the valve 
begins to open at the same end at which 
the piston is then placed, or would be if it 
was attached to the crosshead. Then 
fasten the eccentric on the axle. It is 
usually held by one or two set screws. 
Next turn the engine, in the direction in- 
tended to be run, until the crank pin is on 
the opposite center, and if the opening of 
the valve at the other port is the equal to 
the opening of the first, it proves that 
the valve is correctly set. The lead or 
opening, need not exceed one thirty-second 
of an inch for engines of less than twenty 
horse power, but may be increased in the 
case of larger engines. 

In determining the proper length of the 
valve rod, the eccentric may be left loose 
on the axle and after being connected to 
the valve rod the eccentric may be readily 
moved around on the axle and the extreme 
points of the travel of the valve marked 
on the steam chest or valve face. If the 
points of travel are at equal distances 
from the ports the length of the valve 
rod is correct. If the distances are un- 



equal, the valve rod should be lengthened 
or shortened, as the case may require, half 
the amount of the variation. The ex- 
periment of turning the eccentric around 
on the axle should be repeated and care 
should be taken that the valve rod is ex- 
actly the required length. 

A good method of finding the dead 
centers of stationary engines is by using 
a surface gauge which may be set con- 
veniently on the bed-plate of the engine 
and the pointer adjusted to the center 
of the shaft. The engine can then be 
turned until the center of the crank cor- 
responds to the height of the pointer. In 
the absence of a surface gauge, a bent 
rod of iron, pointed, or a thin board or 
other convenient device adapted for point- 
ing to the center of the shaft, may be 
used. Where the bed-plate of the engine 
cannot be utilized the dead centers can 
readily be found by markings on the 
crosshead and rim of the wheel when 
near the center and moving the engine 
slowly and carefully, catching with a 
tram or compass the same mark on the 
crosshead after it has passed the center. 
The crosshead need not be moved more 
than a quarter of an inch backward and 
forward. Meanwhile the rim of the wheel 



56 



NOTE ON SETTING THE SLIDE VALVE OF A STATIONARY ENGINE. 



will have moved a considerable distance 
and a point exactly between the two mark- 
ings on the rim of the wheel will be the 
dead center. This operation was more 
fully described in our article on the ad- 
justment of the Stephenson shifting link 
gear. 

A direct acting engine, so called be- 
cause of the eccentric acting on the valve 
rod without the intervention of a rocker, 
requires that the eccentric should be set 
ahead of the crank, the exact amount de- 
pending upon the lap of the valve and the 
amount of lead or opening allowed at the 
beginning of the stroke. In the case of an 
engine equipped with a rocker, which is 
an indirect acting engine, the eccentric 
follows the crank pin at a corresponding 
distance. 

It need hardly be reiterated that the 
exact relation of the eccentric to the 
crank, as well as the correct adjustment 
and careful maintenance of all the parts 
of the valve gearing is of the utmost im- 
portance in all kinds of steam engines. 
The exact location of the valve at the 
end of the piston strokes should be occa- 
sionally ascertained with a view to make 
corrections if necessary. In all changes 
it is well to note carefully that the valve 
moves evenly and freely on the valve 
seat. The tendency to twist the valve 
rod in blacksmithing operations is very 
great, and a hasty or careless adjustment 
of any part of the valve gearing, and es- 
pecially of the valve rod, is almost certain 
to be fraught with the most pernicious 
consequences. 

The tendency among engineers to med- 



dle with the valve motion is happily pass- 
ing away. A growth in technical educa- 
tion has hushed the cry for more lead. 
One would think that common sense 
would suggest to any intelligent mechanic 
the fact that a large quantity of steam ad- 
mitted into the end of the cylinder 
toward which the piston was moving .could 
not be other than a hindrance to the pis- 
ton, but so rooted was this mistaken 
idea in the minds of many enginemen 
that the exploded fallacy still lingers in 
the minds of some. 

It could not be expected in this brief 
article to describe the endless variety of 
forms in which the valve gearing of sta- 
tionary engines appear. As we have pre- 
viously stated, a knowledge of the ele- 
mentary principles that govern the rela- 
tion of the valve and piston of all recip- 
rocating engines will naturally lead the 
intelligent mechanic or engineer to a 
ready understanding of any kind of valve 
motion that may come to his attention. 
The introduction of what are known as 
inside admission piston valves on many 
locomotives as well as on stationary en- 
gines does not present any new problem 
to those already familiar with the opera- 
tions of the older sliding valve. The lo- 
cation of the eccentric on the axle may 
readily be found by experiment. In the 
case of an inside admission valve with a 
rocker operating between the valve rod 
and eccentric rod, the location of the 
eccentric on the axle is identical with 
that of a direct acting engine, equipped 
with an outside admission valve. In 
brief, with the proper adjustment of the 



57 



THE VALVE-SETTER'S GUIDE 

valve rod, as has been already stated, merely in the direction of making 

and with the crank pin in either center, the adjustment of the gearing as near. 

the mechanism may be moved until the an approach to perfection as is pos- 

valve begins to open at the proper port, sible in a complex and rapidly moving 

and it will be found that the succeeding engine exerting forces of variable magni- 

operations that may be necessary are tude. 



58 





^o locomotive 

Has long held the reputation of being 

The Most Interesting Paper Published 

It is the best kind of a paper 
FOR BUSY RAILROAD MEN TO READ 

The paper gives in a succinct form 

ALL THE RAILROAD NEWS 

of the month, besides current personal notes and attractive technical 
information. 

Discussion of railroad subjects by 

PRACTICAL RAILROAD MEN 

is a most interesting feature. 

The Air Brake Department and the Electrical Department are 
edited by experts while the Question and Answer Department gives 
correct answers to every question asked. 

THE PAPER IS ADAPTED TO GIVE USEFUL 
INFORMATION TO 

EVERY CLASS OF RAILROAD MEN 

Sample Copies on Application 
TWO DOLLARS PER ANNUM. 

Published monthly by the 

ANGUS SINCLAIR CO., 114 Liberty Street, NEW YORK 



50 



THE ANGUS SINCLAIR COMPANY'S 
STEPHENSON VALVE MOTION MODEL 

SEE PAGES 15 and 25 

29 inches long, 11 inches high, cylinders 3^4 x 4^ inches, 
throw of eccentrics 1 inch, length of link slot A 1 /* inches. 

EVERY PART MADE OF METAL. 

EVERY PART ADJUSTABLE. 

Price, $15.00, or twenty-five subscriptions to Railway and Loco- 
motive Engineering at $2.00 each. 

Is unquestionably the finest model of its kind ever placed 
within the reach of railroad men. 

Valve setting can be learned much more readily on this model 
than on the locomotive itself. All the parts are visible. All the 
parts are readily adjustable. The subject can be studied during 
leisure hours. 

D slide valves or piston valves may be used, the parts being 
interchangeable. 

A thorough knowledge of the valve motion in locomotives is 
indispensable to Engineers and first-class Machinists. An accom- 
plished valve setter outranks his brother engineers or shopmates 
and is in line for sure promotion. Firemen and apprentices should 
study it. Hundreds are already in use in Railway Clubs and 
Schools. It has become an essential educational factor in the train- 
ing of the Twentieth Century Railway Man. 



Sole Manufacturers and Proprietors, 

ANGUS SINCLAIR COMPANY 

114 LIBERTY ST., NEW YORK 



6o 



KB 3 JgjQ 



One copy del. to Cat. Div. 



Ivlv 



